Julian Kinderlerer - Academia.edu (original) (raw)

Papers by Julian Kinderlerer

International Journal of Bio-Medical Computing, 1975

This paper describes a simple program for a desk-top computer which determines the relative conce... more This paper describes a simple program for a desk-top computer which determines the relative concentrations of enzyme-containing intermediates appearing in an enzyme catalysed reaction where the intermediates lie in an unbranched sequence originating and terminating in one enzyme intermediate. This information, the distribution function, then gives the rate equation by the usual means (Wong and Hanes, 1962). The method is rapid and has the advantage that the distribution function may be presented in its complete form or in terms of its dependence on the concentration of the substrates and products. It is also possible to determine the effects of dead-end inhibition.

International Journal Of Medical Informatics, Jul 1, 1984

The two substrate exponential model for a regulatory enzyme (Ainsworth and Gregory, J. Theor. Bio... more The two substrate exponential model for a regulatory enzyme (Ainsworth and Gregory, J. Theor. Biol., 75 (1978) 97-114) can be employed to describe non-hyperbolic relationships between the initial velocity of the catalysed reaction and the concentration of one substrate when the concentration of the second substrate is kept constant, v = f(A)B. The model equation for v = f(A)B predicts the possibility of a maximum, catastrophe and inflections but, because the equation is transcendental, it is not possible to locate the critical points by algebraic analysis. The paper describes an iterative computer program that has been devised to solve this problem.

Journal of Theoretical Biology, May 1, 1982

The paper describes the logic of a computer method for identifying unbranched enzyme kinetic mech... more The paper describes the logic of a computer method for identifying unbranched enzyme kinetic mechanisms on the basis of observed initial velocity and product inhibition patterns (Cleland, 1963). The method establishes initially an acceptable order of reactant addition and release, proceeds to list all the mechanisms consistent with that order and the data, and finally determines which of these can also explain data which require either non-competitive or dead-end inhibition.

International Food Policy Research Institute eBooks, 2005

he aim of this chapter is to address the policy, regulatory, and ethical issues surrounding agric... more he aim of this chapter is to address the policy, regulatory, and ethical issues surrounding agricultural biotechnology. The chapter provides background on the shaping of policy and on regulatory frameworks within the European Union and the United States, among others, as well as outlining the global framework in which all countries have to operate. In addition it summarizes the United Nations-led initiative to assist developing countries to implement biosafety frameworks devised by a specific country for that country. The chapter also highlights the ongoing debate in the areas of environmental protection, public perception and acceptance, and intellectual property rights. The most important reason for addressing the policies of the European Union and the United States on genetically modified organisms rather than the policies of other nations is that they are very different in concept-although in practice, once the regulatory system has been triggered their formal treatment of such organisms is very much the same. The introduction of a new technology such as agricultural biotechnology may depend on the perceived balance between the benefits of the technology and the potential risks to the environment and human health. This chapter aims to put forward the arguments and issues related to the potential benefits of agricultural biotechnology against a background of perceived risks, but it does not seek to provide the answers.

International Journal Of Medical Informatics, 1979

The paper describes a non-linear multiple regression program to analyse data arising from the bin... more The paper describes a non-linear multiple regression program to analyse data arising from the binding of a single ligand by a protein under the assumption that the reaction can be represented by the exponential model for a regulatory enzyme. SOMMAlRE On decrit dans cet article un programme de regression multiple, non lintaire, destink a anaiyser les donnkes concernant la fixation par une prottine dune liaison unique, dans l'hypothtse air la reaction pact etre represent&e par le mod&e exponen-tie1 relatif a une enzyme regulatrice.

International Journal Of Medical Informatics, Jul 1, 1981

The exponential model for a regulatory enzyme describes the relationship between the initial velo... more The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been devised to analyse rate data in terms of the model (Kinderlerer et al., 1981) and, in this report, its performance is examined when presented with experimental initial velocity data taken from the literature. It is shown that the two-ligand exponential model can satisfactorily rationalise experimental data with five linked constants (Ainsworth and Gregory, 1978); as a result the influence of ligand concentrations on the catalysed reactions can be described in rather simple terms.

Biochemical Journal, Feb 1, 1983

The kinetics of rabbit muscle pyruvate kinase were studied in assays at pH 7.4, where the relatio... more The kinetics of rabbit muscle pyruvate kinase were studied in assays at pH 7.4, where the relationships between the initial velocities of the catalysed reaction and the concentrations of substrates ADP, phosphoenolpyruvate and Mg2+ are non-hyperbolic. The data were used to test the applicability of the exponential model for a regulatory enzyme, which has been here extended to describe the behaviour of a three-substrate enzyme. It appears that the data can be represented by the model and as a result permit the conclusion that the substrates influence one another's binding by the same type of charge interactions that are evident in the Michaelis-Menten kinetics of the enzyme observed at pH 6.2. Evidence is also presented indicating that MgADP acts as a dead-end inhibitor of the enzyme at pH 7.4.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C as a function ... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C as a function of the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ and the effector H+ in the pH range 5-6.6. The enzyme was activated by 100 mM-K+ and 32 mM-NH4+ throughout. It was found that the data could be described by the exponential model for a regulatory enzyme. On that basis, it was concluded that the binding of H+ is positively interactive and that the protonated enzyme is catalytically inactive. It was also found that H+ interacts positively with phosphoenolpyruvate but negatively with both ADP and Mg2+.

Chapter 27 Doha Developments: The July Package and Agriculture Julian Kinderlerer and Christian L... more Chapter 27 Doha Developments: The July Package and Agriculture Julian Kinderlerer and Christian Lopez-Silva The most difficult issue for negotiation in the last WTO Round, known as the Doha Development Agenda, has probably been agriculture. The programme of reform has ...

International Journal Of Medical Informatics, Jul 1, 1981

The exponential model for a regulatory enzyme describes the relationship between the initial velo... more The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been devised to analyse rate data in terms of the model (Kinderlerer et al., 1981) and, in this report, its performance is examined when presented with experimental initial velocity data taken from the literature. It is shown that the two-ligand exponential model can satisfactorily rationalise experimental data with five linked constants (Ainsworth and Gregory, 1978); as a result the influence of ligand concentrations on the catalysed reactions can be described in rather simple terms.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C and pH 6.2 as ... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C and pH 6.2 as a function of the concentrations of ADP, phosphoenolpyruvate, Mg2+ and either NH4+ or K+. The data were analysed by the exponential model for four substrates, obtained by extension of the model described by Ainsworth, Kinderlerer & Gregory [(1983) Biochem. J. 209, 401-411]. On that basis, it was concluded that NH4+ binding is almost non-interactive but leads to the appearance of positive interaction in the velocity response to increase in its concentration because of positive interactions with phosphoenolpyruvate and Mg2+. The data obtained with K+ lead to the same conclusions and differ only in suggesting that NH4+ is bound more strongly to the enzyme than is K+. Both data sets are used as the basis for a discussion of the substrate interactions of pyruvate kinase and it appears therefrom that the heterotropic interactions accord with what is known of the events that take place at the active site during catalysis. The paper also reports a determination of the dissociation constants for the NH4+ complexes with ADP and phosphoenolpyruvate and an examination of the simultaneous activation of pyruvate kinase by K+ and NH4+ ions. Manchester (1980). On any horizontal line drawn on the Figure, the distance A-B represents the concentration of Mg2+-Vol. 234 705

Routledge eBooks, Sep 8, 2017

International Journal Of Medical Informatics, Oct 1, 1975

This paper describes a simple program for a desk-top computer which determines the relative conce... more This paper describes a simple program for a desk-top computer which determines the relative concentrations of enzyme-containing intermediates appearing in an enzyme catalysed reaction where the intermediates lie in an unbranched sequence originating and terminating in one enzyme intermediate. This information, the distribution function, then gives the rate equation by the usual means (Wong and Hanes, 1962). The method is rapid and has the advantage that the distribution function may be presented in its complete form or in terms of its dependence on the concentration of the substrates and products. It is also possible to determine the effects of dead-end inhibition.

Global bioethics, 2004

The ability of science to operate effectively within society is dependant on a number of factors.... more The ability of science to operate effectively within society is dependant on a number of factors. Science is totally reliant on the law for its regulation and control, while the boundaries in which science can operate are governed by legal constraints. These boundaries are strongly influenced by society which dictates acceptable levels of morals and ethics in which science can operate. Economic factors must be considered as industry requires reward in order to recoup its research and development investments and continue competing in a competitive and growing market place. Thus the law must reconcile the different tensions raised by science, economics, politics, society and the law itself. This paper looks how this may be achieved at the international, regional and national level.

International Journal Of Medical Informatics, Mar 1, 1987

The paper describes a program (DESCENT) which evaluates the constants of the exponential model fo... more The paper describes a program (DESCENT) which evaluates the constants of the exponential model for a regulatory enzyme with up to four substrates or up to three substrates and one effector. The program operates by repetitive adjustment of the model constants so as to secure a better fit between the observed and calculated initial velocities of reaction. At each adjustment, ail the constants are incremented simultaneously by amounts determined by a steepest descent criterion. The program is tested by arti&iaI data with and without added error and it is shown that good estimates of the constants can be recovered.

Biochemical journal. Cellular aspects, Oct 1, 1970

Biochemical Journal, Feb 1, 1984

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 wh... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 where the relationships between the initial velocities of the catalysed reaction and the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ are non-hyperbolic. The findings were represented empirically by the exponential model for a regulatory enzyme. The analysis shows that ADP, phosphoenolpyruvate and Mg2+ display positive homotropic interaction in their binding behaviour with (calculated) Hill slopes at half-saturation equal to 1.06, 2.35 and 3.11 respectively [Ainsworth (1977) J. Theor. Biol. 68, 391-413]. The direct heterotropic interaction between ADP and phosphoenolpyruvate is small and negative, but the overall interaction between these substrates becomes positive when their positive interactions with Mg2+ are taken into account. The heterotropic interactions of the substrates, though smaller in magnitude, are comparable with those revealed by the rabbit muscle enzyme [Ainsworth, Kinderlerer & Gregory (1983) Biochem. J. 209, 401-411], and it is suggested that they have a common origin in charge interactions within the active site.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 at... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 at 25°C as a function of the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ and the concentration of the effector fructose 1,6-bisphosphate. The enzyme was activated by 100 mM-K+ and 32 mM-NH4+ throughout. It was found that an increase in the fructose bisphosphate concentration from 24 /tM to 1.2 mm brings about a transition from a sigmoidal to a non-inflected form in the relationships v = f([phosphoenolpyruvate]) and v = f([Mg2+]) together with a large increase in the affinity of these substrates for the enzyme. The binding behaviour of ADP is barely affected by the same change in effector concentration. By contrast, increase in fructose bisphosphate concentration below 24 gM increases the affinity of the enzyme for all its substrates and the sigmoidicity ofthe corresponding velocity-substrate-concentration relationships. As a result of this change in behaviour it has been found impossible to represent all the data by the exponential model for a regulatory enzyme, and it is suggested (supported by comparisons with previous work) that the failure may reflect a secondary action of the effector upon the enzyme.

Journal of Evolutionary Biology, Sep 1, 1995

Biochemical Society Transactions, Oct 1, 1980

The following computer programs, for use on microcomputer systems, have been developed to assist ... more The following computer programs, for use on microcomputer systems, have been developed to assist enzyme kinetic studies. (1) A program to determine the rate equation of an enzyme-catalysed reaction involving up to 12 enzyme-containing intermediate complexes (Kinderlerer 8c Ainsworth, 1976). (2) A program to determine the concentration-dependence of the enzyme distribution function required by any unbranched mechanism for an enzyme-catalysed reaction. The program is based on the set nomenclature for enzyme mechanisms (Ainsworth, 1975). (3) A program to determine the parameters of the exponential model for a single-substrate regulatory enzyme (Ainsworth, 1977; Kinderlerer 8c Ainsworth, 1978). (4) A program to calculate the velocityxoncentration relationships of a two-ligand regulatory enzyme according to given parameters of the exponential model (Ainsworth L Gregory, 1978). (5) A program to determine the parameters of the two-ligand exponential model (Ainsworth 8c Gregory, 1978) from measured velocity-concentration data. (6) A program to analyse V,,,.. and K, as functions of pH in terms of the Michaelis pH function for half-ionized enzyme species (Gregory 8c Kinderlerer, 1980). The programs are written in BASIC for a Wang 2200 computer. Listings are available. In addition, two mechanical devices for the determination of enzyme distribution functions are open to inspection (Ainsworth, 1974a,b).

International Journal of Bio-Medical Computing, 1975

This paper describes a simple program for a desk-top computer which determines the relative conce... more This paper describes a simple program for a desk-top computer which determines the relative concentrations of enzyme-containing intermediates appearing in an enzyme catalysed reaction where the intermediates lie in an unbranched sequence originating and terminating in one enzyme intermediate. This information, the distribution function, then gives the rate equation by the usual means (Wong and Hanes, 1962). The method is rapid and has the advantage that the distribution function may be presented in its complete form or in terms of its dependence on the concentration of the substrates and products. It is also possible to determine the effects of dead-end inhibition.

International Journal Of Medical Informatics, Jul 1, 1984

The two substrate exponential model for a regulatory enzyme (Ainsworth and Gregory, J. Theor. Bio... more The two substrate exponential model for a regulatory enzyme (Ainsworth and Gregory, J. Theor. Biol., 75 (1978) 97-114) can be employed to describe non-hyperbolic relationships between the initial velocity of the catalysed reaction and the concentration of one substrate when the concentration of the second substrate is kept constant, v = f(A)B. The model equation for v = f(A)B predicts the possibility of a maximum, catastrophe and inflections but, because the equation is transcendental, it is not possible to locate the critical points by algebraic analysis. The paper describes an iterative computer program that has been devised to solve this problem.

Journal of Theoretical Biology, May 1, 1982

The paper describes the logic of a computer method for identifying unbranched enzyme kinetic mech... more The paper describes the logic of a computer method for identifying unbranched enzyme kinetic mechanisms on the basis of observed initial velocity and product inhibition patterns (Cleland, 1963). The method establishes initially an acceptable order of reactant addition and release, proceeds to list all the mechanisms consistent with that order and the data, and finally determines which of these can also explain data which require either non-competitive or dead-end inhibition.

International Food Policy Research Institute eBooks, 2005

he aim of this chapter is to address the policy, regulatory, and ethical issues surrounding agric... more he aim of this chapter is to address the policy, regulatory, and ethical issues surrounding agricultural biotechnology. The chapter provides background on the shaping of policy and on regulatory frameworks within the European Union and the United States, among others, as well as outlining the global framework in which all countries have to operate. In addition it summarizes the United Nations-led initiative to assist developing countries to implement biosafety frameworks devised by a specific country for that country. The chapter also highlights the ongoing debate in the areas of environmental protection, public perception and acceptance, and intellectual property rights. The most important reason for addressing the policies of the European Union and the United States on genetically modified organisms rather than the policies of other nations is that they are very different in concept-although in practice, once the regulatory system has been triggered their formal treatment of such organisms is very much the same. The introduction of a new technology such as agricultural biotechnology may depend on the perceived balance between the benefits of the technology and the potential risks to the environment and human health. This chapter aims to put forward the arguments and issues related to the potential benefits of agricultural biotechnology against a background of perceived risks, but it does not seek to provide the answers.

International Journal Of Medical Informatics, 1979

The paper describes a non-linear multiple regression program to analyse data arising from the bin... more The paper describes a non-linear multiple regression program to analyse data arising from the binding of a single ligand by a protein under the assumption that the reaction can be represented by the exponential model for a regulatory enzyme. SOMMAlRE On decrit dans cet article un programme de regression multiple, non lintaire, destink a anaiyser les donnkes concernant la fixation par une prottine dune liaison unique, dans l'hypothtse air la reaction pact etre represent&e par le mod&e exponen-tie1 relatif a une enzyme regulatrice.

International Journal Of Medical Informatics, Jul 1, 1981

The exponential model for a regulatory enzyme describes the relationship between the initial velo... more The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been devised to analyse rate data in terms of the model (Kinderlerer et al., 1981) and, in this report, its performance is examined when presented with experimental initial velocity data taken from the literature. It is shown that the two-ligand exponential model can satisfactorily rationalise experimental data with five linked constants (Ainsworth and Gregory, 1978); as a result the influence of ligand concentrations on the catalysed reactions can be described in rather simple terms.

Biochemical Journal, Feb 1, 1983

The kinetics of rabbit muscle pyruvate kinase were studied in assays at pH 7.4, where the relatio... more The kinetics of rabbit muscle pyruvate kinase were studied in assays at pH 7.4, where the relationships between the initial velocities of the catalysed reaction and the concentrations of substrates ADP, phosphoenolpyruvate and Mg2+ are non-hyperbolic. The data were used to test the applicability of the exponential model for a regulatory enzyme, which has been here extended to describe the behaviour of a three-substrate enzyme. It appears that the data can be represented by the model and as a result permit the conclusion that the substrates influence one another's binding by the same type of charge interactions that are evident in the Michaelis-Menten kinetics of the enzyme observed at pH 6.2. Evidence is also presented indicating that MgADP acts as a dead-end inhibitor of the enzyme at pH 7.4.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C as a function ... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C as a function of the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ and the effector H+ in the pH range 5-6.6. The enzyme was activated by 100 mM-K+ and 32 mM-NH4+ throughout. It was found that the data could be described by the exponential model for a regulatory enzyme. On that basis, it was concluded that the binding of H+ is positively interactive and that the protonated enzyme is catalytically inactive. It was also found that H+ interacts positively with phosphoenolpyruvate but negatively with both ADP and Mg2+.

Chapter 27 Doha Developments: The July Package and Agriculture Julian Kinderlerer and Christian L... more Chapter 27 Doha Developments: The July Package and Agriculture Julian Kinderlerer and Christian Lopez-Silva The most difficult issue for negotiation in the last WTO Round, known as the Doha Development Agenda, has probably been agriculture. The programme of reform has ...

International Journal Of Medical Informatics, Jul 1, 1981

The exponential model for a regulatory enzyme describes the relationship between the initial velo... more The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been devised to analyse rate data in terms of the model (Kinderlerer et al., 1981) and, in this report, its performance is examined when presented with experimental initial velocity data taken from the literature. It is shown that the two-ligand exponential model can satisfactorily rationalise experimental data with five linked constants (Ainsworth and Gregory, 1978); as a result the influence of ligand concentrations on the catalysed reactions can be described in rather simple terms.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C and pH 6.2 as ... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied at 25°C and pH 6.2 as a function of the concentrations of ADP, phosphoenolpyruvate, Mg2+ and either NH4+ or K+. The data were analysed by the exponential model for four substrates, obtained by extension of the model described by Ainsworth, Kinderlerer & Gregory [(1983) Biochem. J. 209, 401-411]. On that basis, it was concluded that NH4+ binding is almost non-interactive but leads to the appearance of positive interaction in the velocity response to increase in its concentration because of positive interactions with phosphoenolpyruvate and Mg2+. The data obtained with K+ lead to the same conclusions and differ only in suggesting that NH4+ is bound more strongly to the enzyme than is K+. Both data sets are used as the basis for a discussion of the substrate interactions of pyruvate kinase and it appears therefrom that the heterotropic interactions accord with what is known of the events that take place at the active site during catalysis. The paper also reports a determination of the dissociation constants for the NH4+ complexes with ADP and phosphoenolpyruvate and an examination of the simultaneous activation of pyruvate kinase by K+ and NH4+ ions. Manchester (1980). On any horizontal line drawn on the Figure, the distance A-B represents the concentration of Mg2+-Vol. 234 705

Routledge eBooks, Sep 8, 2017

International Journal Of Medical Informatics, Oct 1, 1975

This paper describes a simple program for a desk-top computer which determines the relative conce... more This paper describes a simple program for a desk-top computer which determines the relative concentrations of enzyme-containing intermediates appearing in an enzyme catalysed reaction where the intermediates lie in an unbranched sequence originating and terminating in one enzyme intermediate. This information, the distribution function, then gives the rate equation by the usual means (Wong and Hanes, 1962). The method is rapid and has the advantage that the distribution function may be presented in its complete form or in terms of its dependence on the concentration of the substrates and products. It is also possible to determine the effects of dead-end inhibition.

Global bioethics, 2004

The ability of science to operate effectively within society is dependant on a number of factors.... more The ability of science to operate effectively within society is dependant on a number of factors. Science is totally reliant on the law for its regulation and control, while the boundaries in which science can operate are governed by legal constraints. These boundaries are strongly influenced by society which dictates acceptable levels of morals and ethics in which science can operate. Economic factors must be considered as industry requires reward in order to recoup its research and development investments and continue competing in a competitive and growing market place. Thus the law must reconcile the different tensions raised by science, economics, politics, society and the law itself. This paper looks how this may be achieved at the international, regional and national level.

International Journal Of Medical Informatics, Mar 1, 1987

The paper describes a program (DESCENT) which evaluates the constants of the exponential model fo... more The paper describes a program (DESCENT) which evaluates the constants of the exponential model for a regulatory enzyme with up to four substrates or up to three substrates and one effector. The program operates by repetitive adjustment of the model constants so as to secure a better fit between the observed and calculated initial velocities of reaction. At each adjustment, ail the constants are incremented simultaneously by amounts determined by a steepest descent criterion. The program is tested by arti&iaI data with and without added error and it is shown that good estimates of the constants can be recovered.

Biochemical journal. Cellular aspects, Oct 1, 1970

Biochemical Journal, Feb 1, 1984

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 wh... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 where the relationships between the initial velocities of the catalysed reaction and the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ are non-hyperbolic. The findings were represented empirically by the exponential model for a regulatory enzyme. The analysis shows that ADP, phosphoenolpyruvate and Mg2+ display positive homotropic interaction in their binding behaviour with (calculated) Hill slopes at half-saturation equal to 1.06, 2.35 and 3.11 respectively [Ainsworth (1977) J. Theor. Biol. 68, 391-413]. The direct heterotropic interaction between ADP and phosphoenolpyruvate is small and negative, but the overall interaction between these substrates becomes positive when their positive interactions with Mg2+ are taken into account. The heterotropic interactions of the substrates, though smaller in magnitude, are comparable with those revealed by the rabbit muscle enzyme [Ainsworth, Kinderlerer & Gregory (1983) Biochem. J. 209, 401-411], and it is suggested that they have a common origin in charge interactions within the active site.

Biochemical Journal, Mar 15, 1986

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 at... more The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 at 25°C as a function of the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ and the concentration of the effector fructose 1,6-bisphosphate. The enzyme was activated by 100 mM-K+ and 32 mM-NH4+ throughout. It was found that an increase in the fructose bisphosphate concentration from 24 /tM to 1.2 mm brings about a transition from a sigmoidal to a non-inflected form in the relationships v = f([phosphoenolpyruvate]) and v = f([Mg2+]) together with a large increase in the affinity of these substrates for the enzyme. The binding behaviour of ADP is barely affected by the same change in effector concentration. By contrast, increase in fructose bisphosphate concentration below 24 gM increases the affinity of the enzyme for all its substrates and the sigmoidicity ofthe corresponding velocity-substrate-concentration relationships. As a result of this change in behaviour it has been found impossible to represent all the data by the exponential model for a regulatory enzyme, and it is suggested (supported by comparisons with previous work) that the failure may reflect a secondary action of the effector upon the enzyme.

Journal of Evolutionary Biology, Sep 1, 1995

Biochemical Society Transactions, Oct 1, 1980

The following computer programs, for use on microcomputer systems, have been developed to assist ... more The following computer programs, for use on microcomputer systems, have been developed to assist enzyme kinetic studies. (1) A program to determine the rate equation of an enzyme-catalysed reaction involving up to 12 enzyme-containing intermediate complexes (Kinderlerer 8c Ainsworth, 1976). (2) A program to determine the concentration-dependence of the enzyme distribution function required by any unbranched mechanism for an enzyme-catalysed reaction. The program is based on the set nomenclature for enzyme mechanisms (Ainsworth, 1975). (3) A program to determine the parameters of the exponential model for a single-substrate regulatory enzyme (Ainsworth, 1977; Kinderlerer 8c Ainsworth, 1978). (4) A program to calculate the velocityxoncentration relationships of a two-ligand regulatory enzyme according to given parameters of the exponential model (Ainsworth L Gregory, 1978). (5) A program to determine the parameters of the two-ligand exponential model (Ainsworth 8c Gregory, 1978) from measured velocity-concentration data. (6) A program to analyse V,,,.. and K, as functions of pH in terms of the Michaelis pH function for half-ionized enzyme species (Gregory 8c Kinderlerer, 1980). The programs are written in BASIC for a Wang 2200 computer. Listings are available. In addition, two mechanical devices for the determination of enzyme distribution functions are open to inspection (Ainsworth, 1974a,b).