Marko Vitas - Academia.edu (original) (raw)

Papers by Marko Vitas

The Journal of Steroid Biochemistry and Molecular Biology, Nov 1, 1997

Progesterone biotra:nsformation was examined in relation to hydroxylating and dehydrogenating enz... more Progesterone biotra:nsformation was examined in relation to hydroxylating and dehydrogenating enzymes of Cochliobolus lunatus. 11]~-hydroxysteroid dehydrogenase activity (1 lfl-HSD) was located in cytosoHc fraction and was NADP-dependent, inducible by progesterone and apparently unidirectional. Several iinhibitors of l lff-hydroxysteroid dehydrogenase were tested; furosemide, glycyrrhizic-acid and carbenoxolone did not influence the dehydrogenation of llfl-hydroxy-4-pregnene-3,20-dione to 4-pregnene-3,11,20-trione, although grapefruit juice significantly reduced the rate of progesterone hydroxylation.

International Journal of Molecular Sciences, May 13, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Int. J. Mol. Sci., 2023

Foundations of Chemistry, 2016

Explaining the emergence of life is perhaps central and the most challenging question in modern s... more Explaining the emergence of life is perhaps central and the most challenging question in modern science. Within this area of research, the emergence and evolution of the genetic code is supposed to be a critical transition in the evolution of modern organisms. The canonical genetic code is one of the most dominant aspects of life on this planet, and thus studying its origin is critical to understanding the evolution of life, including life’s emergence. In this sense it is possible to view the ribosome as a digital-to-analogue information converter. Why the translation apparatus evolved, is one of the enduring mysteries of molecular biology. Assuming the hypothesis that during the emergence of life evolution had to first involve autocatalytic systems, which only subsequently acquired the capacity of genetic heredity, in the present article we discuss some aspects and causes of the possible emergence of digital, discrete information arising from analogue information realized in the intra- and inter-molecular interactions throughout molecular evolution. How such reverse translation was achieved at a molecular level is still unclear. The results of such debates and investigations might shift current biological paradigms and might also have a momentous significance for modern philosophy in understanding our place in the universe.

Origins of Life and Evolution of Biospheres

Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 2018

The origin of translation is critical for understanding the evolution of life, including the orig... more The origin of translation is critical for understanding the evolution of life, including the origins of life. The canonical genetic code is one of the most dominant aspects of life on this planet, while the origin of heredity is one of the key evolutionary transitions in living world. Why the translation apparatus evolved is one of the enduring mysteries of molecular biology. Assuming the hypothesis, that during the emergence of life evolution had to first involve autocatalytic systems which only subsequently acquired the capacity of genetic heredity, we propose and discuss possible mechanisms, basic aspects of the emergence and subsequent molecular evolution of translation and ribosomes, as well as enzymes as we know them today. It is possible, in this sense, to view the ribosome as a digital-to-analogue information converter. The proposed mechanism is based on the abilities and tendencies of short RNA and polypeptides to fold and to catalyse biochemical reactions. The proposed mec...

Bio Systems, Jan 7, 2017

A procedure for maximization of the density of entropy production in a single stationary two-step... more A procedure for maximization of the density of entropy production in a single stationary two-step enzyme reaction is developed. Under the constraints of mass conservation, fixed equilibrium constant of a reaction and fixed products of forward and backward enzyme rate constants the existence of maximum in the density of entropy production is demonstrated. In the state with maximal density of entropy production the optimal enzyme rate constants, the stationary concentrations of the substrate and the product, the stationary product yield as well as the stationary reaction flux are calculated. The test, whether these calculated values of the reaction parameters are consistent with their corresponding measured values, is performed for the enzyme Glucose Isomerase. It is found that calculated and measured rate constants agree within an order of magnitude, whereas the calculated reaction flux and the product yield differ from their corresponding measured values for less than 20 % and 5 %, ...

Modern science still did not give us a satisfactory empirical explanation of increasing complexit... more Modern science still did not give us a satisfactory empirical explanation of increasing complexity in living beings through the evolutionary history. This question poses itself when comparing simple prokaryotic cells with more complex eukaryotic cells or comparing these with animals or plants or the most complex phenomena, e.g. consciousness and human language. The proposed thesis defends the hypothesis that at the beginning in the origins of life the evolution had to first involve autocatalytic systems, which only subsequently acquired the capacity of genetic heredity.

Modern science has still not given us a satisfactory empirical explanation of the increasing comp... more Modern science has still not given us a satisfactory empirical explanation of the increasing complexity in living beings through evolutionary history, though whether or not the complexity increases in biological evolution is a hotly debated topic and no agreed-upon definitions of the complexity exist. Nevertheless, this poses the question when comparing simple prokaryotic cells with more complex eukaryotic cells or comparing these with animals or plants or the most complex phenomena, e.g. consciousness and human language. The question of how life actually came into existence is definitely important in this respect. Assuming the hypothesis that in the beginning of the origins of life evolution had to first involve autocatalytic systems which only subsequently acquired the capacity of genetic heredity, we discuss in the present article the possible emergence of digital, discrete information arising from analogue information stored in the intra and intermolecular interactions throughout the molecular evolution. Explaining the origin of life is perhaps central and the most challenging question in modern science. The results of such debates and investigations might shift current biological paradigms and might also have a momentous significance for modern philosophy in understanding our place in universe.

Abstract: Modern science has still not given us a satisfactory empirical explanation of the incre... more Abstract: Modern science has still not given us a satisfactory empirical explanation of the increasing complexity in living beings through evolutionary history, though whether or not the complexity increases in biological evolution is a hotly debated topic and no agreed-upon definitions of the complexity exist. Nevertheless, this poses the question when comparing simple prokaryotic cells with more complex eukaryotic cells or comparing these with animals or plants or the most complex phenomena, e.g. consciousness and human language. The question of how life actually came into existence is definitely important in this respect. Assuming the hypothesis that in the beginning of the origins of life evolution had to first involve autocatalytic systems which only subsequently acquired the capacity of genetic heredity, we discuss in the present article the possible emergence of digital, discrete information arising from analogue information stored in the intra and intermolecular interactions throughout the molecular evolution. Explaining the origin of life is perhaps central and the most challenging question in modern science. The results of such debates and investigations might shift current biological paradigms and might also have a momentous significance for modern philosophy in understanding our place in universe.

This essay was published in Slovene language in June 2011: Vitas M. O teoriji razvoja vrst a pomo... more This essay was published in Slovene language in June 2011: Vitas M. O teoriji razvoja vrst a pomočjo naravne selekcije, Apokalipsa: revija za preboj v živo kulturo, 152, pp. 113-122, 2011. =================================================================== ABSTRACT Modern science still did not give us a satisfactory empirical explanation of increasing complexity in living beings through the evolutionary history. This question poses itself when comparing simple prokaryotic cells with more complex eukaryotic cells or comparing these with animals or plants or the most complex phenomena, e.g. consciousness and human language. The proposed thesis defends the hypothesis that at the beginning in the origins of life the evolution had to first involve autocatalytic systems, which only subsequently acquired the capacity of genetic heredity.

Journal of Biotechnology, 1995

Progesterone hydroxylation was examined in relation to P450 enzymes present in the microsomal fra... more Progesterone hydroxylation was examined in relation to P450 enzymes present in the microsomal fraction of Cochliobolus lunate. The bioconversion resulted in metabolites of progesterone becoming located in the media rather than the mycelium where progesterone was concentrated. P450 content did not vary with exposure to progesterone, but the detection of higher inducible activity for progesterone metabolism suggested only a small proportion of the P45Os present were involved. High efficiency bioconversion of progesterone into mono-and dihydroxy-products was observed for microsomal fractions containing the induced activity. * Corresponding author. making purification difficult to assess. Also, there is probably low homology with mammalian steroid hydroxylases precluding their use as hybridisation probes. We are interested in the molecular biology of these systems and report here on the P450 system of Cochliobolus lunatus, its inducibility by progesterone and the in vitro activity of the monooxygenase system.

Journal of Steroid Biochemistry and Molecular Biology, 1994

Chemosphere, 1999

We investigated the hypothesis that the endogenous role of the commercially important inducible s... more We investigated the hypothesis that the endogenous role of the commercially important inducible steroid hydroxylase cytochrome P450s of fungi was in defense against plant toxophores/secondary metabolites. Two plant defense compounds, the aglycones tomatidine and solanidine, the steroidal glycoalkaloid alpha-tomatine and the triterpene saponin 15-escin were tested as inducers of 1 ll3/14ct-steroid hydroxylase in the filamentous fungus Cochliobolus lunatus. The extracts of saponins from the roots of Primula veris and green oat leaves were also tested as inducers of l ll3/14ct-hydroxylation activity in progesterone biotransformation with the same fungus. Induction of steroid hydroxylase and inhibition of activity in some cases support our hypothesis that their endogenous function is in biochemical defence against secondary metabolites. 4-Pregnene-3,11,20-trione was added as a substrate for biotransformation with C. lunatus. We isolated from culture broth 14~-hydroxy-4-pregnene-3,11,20-trione, and the hitherto unreported compounds, 7ct,14ct-dihydroxy-4-pregnene-3,11,20-trione and 7a-hydroxy-pregna-4,8(14)-diene-3,11,20-trione.

Yeast, 1999

The fungal biotransformation of steroids is of applied interest due to the economic importance of... more The fungal biotransformation of steroids is of applied interest due to the economic importance of such stereo-and regiospecific reactions and also in the context of ergosterol pathway engineering to produce vitamin D and steroidal products. In Schizosaccharomyces pombe no steroid hydroxylation as is found in filamentous fungi was observed, but a cytosolic NAD(H)/NADP(H)-dependent hydroxysteroid dehydrogenase activity was identified. Progesterone was reduced at the 4 double bond (in vivo only) as well as at the C-3 and C-20 keto groups. Testosterone and 4-androstene-3,17-dione were interconverted and 5 -pregnane-3,20-dione and 5 -pregnane-3,20-dione were reduced to 3-hydroxy products. The reactions were sometimes reversible and showed regio-and stereo specificity. In S. pombe more than one steroid dehydrogenase homologue is likely to occur, as has been observed in Saccharomyces cerevisiae. Our findings indicate that genes encoding soluble proteins should be examined as candidates for actual steroid dehydrogenase activity.

Journal of Steroid Biochemistry and Molecular Biology, 1997

Phytochemistry, 1995

The filamentous fungus Paecilomyces lilacinus converts progesterone to more polar compounds by a ... more The filamentous fungus Paecilomyces lilacinus converts progesterone to more polar compounds by a side-chain cleavage reaction. We have investigated the role of cytochrome P-450 in this mono-oxygenase reaction and confirmed the involvement of other cytosolic enzymes. The activity was found to be NADPH-dependent and inducible by pre-exposure of mycelium to progesterone.

Physiological and Molecular Plant Pathology, 1999

The inducement of commercially important steroid 11α-hydroxylation in the filamentous fungus Rhiz... more The inducement of commercially important steroid 11α-hydroxylation in the filamentous fungus Rhizopus nigricans by several plant saponins and saponin aglycones was tested. The α-tomatine derived aglycone tomatidine and a saponin rich Primula eris root extract were found to be effective inducers of progesterone 11α-hydroxylation in this saprophytic fungus. Furthermore, the transformation of progesterone to 5αpregnane-3,6,20-trione was detected after pre-incubation with these plant constituents. However, the progesterone 11α-hydroxylase activity remained near the constitutive level after treatment of R. nigricans with solanidine, oat-leaf extract and its β-glucosidase treated derivative, while the presence of β-escin and especially α-tomatine lowered the transformation capability of mycelia.