Enzymes Research Papers - Academia.edu (original) (raw)

Microfluidic biosensing systems with enzyme-based detection have been extensively studied in the last years owing to features such as high specificity, a broad range of analytes and a high degree of automation. This review gives an... more

Microfluidic biosensing systems with enzyme-based detection have been extensively studied in the last years owing to features such as high specificity, a broad range of analytes and a high degree of automation. This review gives an overview of the most important factors associated with these systems. In the first part, frequently used immobilization protocols such as physisorption and covalent bonding and detection techniques such as amperometry and fluorescence measurements are discussed with respect to effort, lifetime and measurement range. The Michaelis-Menten model describing the kinetics of enzymatic reactions, the role of redox mediators and the limitations of the linear measurement range of enzymatic sensors are introduced. Several possibilities of extending the linear measurement range in microfluidic systems such as diffusion-limiting membranes and the flow injection setup are presented. Regarding the integration of enzymes into microfluidic systems during the fabrication ...

It is widely considered that a possible advantage of metabolite channelling, in which a product of an enzyme is transferred to the next enzyme in a metabolic pathway without being released to the ‘bulk’ solution, is that channelling can... more

It is widely considered that a possible advantage of metabolite channelling, in which a product of an enzyme is transferred to the next enzyme in a metabolic pathway without being released to the ‘bulk’ solution, is that channelling can decrease the steady-state concentrations of ‘pool’ intermediates. This then spares the limited solvent capacity of the cell, and reduces the loss of pathway flux due to leakage or instability of the free intermediate. Recently, however, based on simulations of a particular model of a ‘dynamic’ channel, Cornish-Bowden [“Failure of channelling to maintain low concentrations of metabolic intermediates” (1991) Eur. J. Biochem. 195, 103–108] has argued that this is not in fact the case; his simulations indicated that the channel was rather ineffective at decreasing the concentration of the pool intermediate, and in some cases actually increased it. However, although his simulations were restricted to very specific thermodynamic and kinetic parameters, he generalised his conclusions, arguing that “channelling has no effect on the free concentration of a channelled intermediate in a pathway”.By showing that, for a number of kinetic cases, the concentration of the pool intermediate did decrease substantially with increased channelling, we demonstrate here that the conclusion of Cornish-Bowden is not correct. In particular, if the reaction catalysed by the enzymes forming the channel has an equilibrium constant K higher than 1, and if the enzyme removing the product of the channel reaction is kinetically competent, channelling in the model system studied by Cornish-Bowden (1991) can decrease the steady-state concentration of the pool by a factor of 1000, independently of the mechanism of the terminal reaction and under conditions of essentially constant overall flux. If the channel is a ‘static’ channel, the decrease in the pool can be to arbitrarily low levels. This conclusion also holds for a system in which other reactions may consume the pool intermediate. Thus, channelling can maintain metabolite concentrations at low levels.

Salinity is one of the main environmental stresses, and it affects potato growth and productivity in arid and semiarid regions by disturbing physiological process, such as the photosynthesis rate, the absorption of essential nutrients and... more

Salinity is one of the main environmental stresses, and it affects potato growth and productivity in arid and semiarid regions by disturbing physiological process, such as the photosynthesis rate, the absorption of essential nutrients and water, plant hormonal functions, and vital metabolic pathways. Few studies are available on the application of combined nanomaterials to mitigate salinity stress on potato plants (Solanum tuberosum L. cv. Diamont). In order to assess the effects of the sole or combined application of silicon (Si) and potassium (K) nanoparticles and biochar (Bc) on the agro-physiological properties and biochemical constituents of potato plants grown in saline soil, two open-field experiments were executed on a randomized complete block design (RCBD), with five replicates. The results show that the biochar application and nanoelements (n-K and n-Si) significantly improved the plant heights, the fresh and dry plant biomasses, the numbers of stems/plant, the leaf relat...

We have investigated the biotechnological potential of Arctic marine bacteria for their ability to produce a broad spectrum of cold-active enzymes. Marine bacteria exhibiting these features are of great interest for both fundamental... more

We have investigated the biotechnological potential of Arctic marine bacteria for their ability to produce a broad spectrum of cold-active enzymes. Marine bacteria exhibiting these features are of great interest for both fundamental research and industrial applications. Macrobiota, water and sediment samples have been collected during 2010 and 2011 expeditions around the Lofoten and Svalbard islands. Bacteria were isolated from this material and identified through 16S rRNA gene sequence analysis for the purpose of establishing a culture collection of marine Arctic bacteria. Herein, we present the functional screening for different extracellular enzymatic activities from 100 diversely chosen microbial isolates incubated at 4 and 20 °C. The production of esterase/lipase, DNase, and protease activities were revealed in 67, 53, and 56% of the strains, respectively, while 41, 23, 9, and 7% of the strains possessed amylase, chitinase, cellulase, and xylanase activities, respectively. Our ...

Extreme environments merit special attention and significance because of the possible existence of thermophilic microorganisms in such ecological niches. Keeping this in mind indigenous stove ash samples were explored for extremophilic... more

Extreme environments merit special attention and significance because of the possible existence of thermophilic microorganisms in such ecological niches. Keeping this in mind indigenous stove ash samples were explored for extremophilic bacteria in term of their biodiversity. Accordingly, this study reports 37 bacterial isolates from the local wood run oven (Tandoor) ash samples. All the isolated strains belong to genus Bacillus on the bases of morpho-cultural and biochemical considerations. The average temperature tolerance profile was >45°C thereby, indicating towards the thermophilic nature of the isolated strains. The Bacillus isolates were screened for 10 different hydrolytic enzymes (cellulase, xylanase, amylase, pectinase, caseinase, keratinase, lipase, esterase, dextranase and β-galactosidase) by plate screening method using the medium incorporated with specific substrate(s). It was found that keratinase was produced by all the isolates while, 36 (97.2%) isolates showed ca...

It is no longer necessary to use dialkylzinc reagents to obtain enantioselectivities >95% in the copper-catalyzed asymmetric conjugate addition of organometallic compounds to cyclic enones. We now report how this can be accomplished by... more

It is no longer necessary to use dialkylzinc reagents to obtain enantioselectivities >95% in the copper-catalyzed asymmetric conjugate addition of organometallic compounds to cyclic enones. We now report how this can be accomplished by using inexpensive and readily available Grignard reagents. Screening of bidentate ligands provided outstanding results with copper complexes of commercially available chiral ferrocenyl-based diphosphines, in particular TaniaPhos and JosiPhos derivatives. These catalysts tolerate a range of Grignard reagents and different cyclic enones as substrates, leading to high regioselectivities and unprecedented enantioselectivities. Moreover, the reactions are successful with moderate catalyst loading (5 mol %) under mild conditions and in the absence of additives.

The toxic effects of i.p. administered n-hexane and n-heptane on biochemical processes in rat liver, as indicated by the increase in alkaline phosphatase activity and decrease in FDP aldolase activity, and their reflection on blood... more

The toxic effects of i.p. administered n-hexane and n-heptane on biochemical processes in rat liver, as indicated by the increase in alkaline phosphatase activity and decrease in FDP aldolase activity, and their reflection on blood chemistry, were studied. Serum cholinesterase activity and albumin and cholesterol content showed statistically significant decreases with the increase in FDP aldolase activity. The significance of the findings is discussed.

Objective: To compare the enzyme activity of different presentations of papain solution to validate in-house preparations. Methods: Two papain solutions were prepared, and the third presentation was a commercial solution. Tests were... more

Objective: To compare the enzyme activity of different presentations of papain solution to validate in-house preparations. Methods: Two papain solutions were prepared, and the third presentation was a commercial solution. Tests were carried out with samples of red cells typed as weak RhD. Results: In-house prepared papain solutions showed similar enzyme reactivity, and statistically no differences compared to the enzyme activity of the commercial solution. Conclusion: Evaluating the cost-benefit ratio, the in-house prepared papain solutions present more economic advantages, and can be incorporated into immunohematological routines as a way to cope with periods of financial crisis and cost-containment policies.

The present research is intended to explore a new dimension for the management of knee joint osteoarthritis. This study resulted in encouraging results for the administration of enzymes (bromelain & papain) supplementation along with... more

The present research is intended to explore a new dimension for the management of knee joint osteoarthritis. This study resulted in
encouraging results for the administration of enzymes (bromelain & papain) supplementation along with physical therapy measures
for the management of knee joint arthritis. As therapeutic exercises are effective but slow in commencement, therefore such remedy is
required which can accelerate the recovery period. These two methods of alternative medicine fulfill the need particularly in
associations between pain and disability (functional status).

Development of artificial enzymes designed for industrial plants that could convert carbon dioxide into carbonates, with the ultimate aim of reducing CO2 emissions. Enzymes are biological catalysts that accelerate chemical reactions, such... more

Development of artificial enzymes designed for industrial plants that could convert carbon dioxide into carbonates, with the ultimate aim of reducing CO2 emissions. Enzymes are biological catalysts that accelerate chemical reactions, such as the conversion of gaseous carbon dioxide (CO2) into carbonates. Carbonates are the basic component of coral reefs, mollusc shells, geological platforms and kidney stones. Although naturally occurring enzymes would be ideal for converting human-generated CO2 emissions into carbonates, they are generally incapable of coping with the extreme conditions of industrial plants. Ernesto and colleagues are now developing artificial enzymes that can withstand the harsh environments of industrial plants while accelerating chemical reactions. His team ultimately aims to create a clean, cheap, practical and socially responsible solution for global warming by reducing CO2 emissions. "We believe that our novel artificial enzymes will be the first tailor-made enzymes for industrial plants to produce carbonates," says Dr Hernandez. So far, Dr Hernandez and his colleagues have built an artificial environment composed of chimney-like equipment, measuring 1.5 metres in height and 15 centimetres in diameter, that mimics the smoke released by power plants. Using the artificial environment, the researchers will ensure that their artificial enzymes can function properly under extreme conditions consisting of hot, corrosive, poisonous and sticky smoke as well as soot and other gases produced by power plants. The team is basing the development of its artificial enzyme on naturally occurring carbonic anhydrase (CA), which accelerates the conversion of CO2 into carbonates. Carbonic anhydrase is capable of turning CO2 molecules into carbonates at a rate of one million molecules per second. However, "the enzyme's CO2 conversion rate slows down dramatically under industrial conditions," Dr Hernandez points out. He and his colleagues are now engineering artificial enzymes based on natural CA, using directed evolution techniques. Their first step involves the creation of a library of diverse genes that encode for carbonic anhydrases. "This library includes sequences of unique forms of carbonic anhydrases recently found near deep-ocean chimneys (hydrothermal vents)," says Dr Hernandez. The team plans to modify and multiply the genes encoding for carbonic anhydrases using a molecular technique called random mutagenesis. The researchers will then place the mutated genes in the artificial environment to see which ones are most effective at converting carbon dioxide into carbonates. The best mutations will then be put through the modification and multiplication processes again. The researchers will repeat the whole process until they have isolated a mutated gene encoding for recombinant carbonic anhydrase that can convert CO2 into carbonates under industrial conditions. With the help of artificial enzymes, CO2-converted carbonates could be used in everything from baking soda and chalk to Portland cement and lime manufacturing.