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E M Logvinenko

Publications and source records attributed to E M Logvinenko.

32 records · Page 2Linked to original sources
PubMedDate not supplied

[Properties of 2,5-diamino-4-oxy-6-ribosylaminopyrimidine-5'- phosphate reductase, a enzyme of the second stage of flavinogenesis in Pichia guilliermondii yeasts].

2,5-Diamino-4-oxy-6-ribosylaminopyrimidine-5'-phosphate reductase has been isolated from cells of Pichia guilliermondii and subjected to 20-fold purification by treating extracts with streptomycin sulphate, frationating proteins (NH4)2SO4 at 45-75% of saturation and chromatography on blue sepharose CL-6B. The use of gel filtration through Sephadex G-150 and chromatography on DEAE-cellulose proved to be less effective for the enzyme purification. It has been established that it is 2,5-diamino-4-oxy-6-ribosylaminopyrimidine-5-phosphate but not its dephosphorylated form that is the substrate of the given reductase; Km is equal to 7.10(-5) M. The reaction proceeds in the presence of NADPH or NADH. The enzyme affinity to NADPH (Km = 4.7.10(-5) M) is approximately one order higher than that to NADPH (Km = 5.5.10(-4) M). The enzyme manifests the optimum of action at pH 7.2 and the temperature of 37 degrees C; the molecular weight is 140 kD. EDTA as well as flavins in the concentration of 1.10(-3) M exert no effect on the reductase activity. The enzyme is labile at 4 degrees C and is inactivated in the frozen state at -15 degrees C. The 2.5-diamino-4-oxy-6-ribosylaminopyrimidine-5'-phosphate reductase has been also revealed in Torulopsis candida, Debaryomyces klöckeri, Schwanniomyces occidentalis, Eremothecium ashbyii (flavinogenic species) and Candida utilis. Aspergillus nidulans, Neurospora crassa (nonflavinogenic species). The synthesis of this enzyme contrary to other enzymes of the riboflavin biosynthesis is not regulated in flavinogenic yeast by iron ions.

Chromatography, DEAE-Cellulose↗
PubMedDate not supplied

[Regulation of the activity and synthesis of enzymes participating in the formation of 6,7-dimethyl-8-ribityllumazine, a riboflavin precursor in yeast].

The properties of two flavinogenesis enzymes--synthase of the aliphatic precursor of riboflavin (APR-synthase) and 6.7-dimethyl-8-ribityllumazinesynthase (DMRL-synthase) of Pichia guilliermondii. It is established that DMRL-synthase, uses APR as a substrate which contains, evidently, a phosphate group. The value of Km for APR is equal to 0.7.10(-5) M, for 2.4-dihydroxy-5-amino-6-ribitylaminopyrimidine--1.25.10(-5) M. It is riboflavin but not FAD that inhibits the activity of DMRL-synthase; the value (I)0.5 is equal to 2.10(-5) M. DMRL, riboflavin, flavin mononucleotide and FAD do not affect the APR-synthase activity. In iron-deficient cells of P. guilliermondii, Torulopsis candida, Debaryomyces klöckeri and Schwanniomyces occidentalis realizing the oversynthesis of riboflavin there occurs derepression of DMRL-synthase and APR-synthase.

Candida↗
PubMedDate not supplied

[Supersynthesis of flavins in microorganisms and its molecular mechanism (review of the literature)].

The present review discusses the significance of fundamental research into regulation of flavin biosynthesis for development of the knowledge about mechanisms of overproduction of these compounds and their manufacturing. The pathways of riboflavin, FMN and FAD biosyntheses and their regulation in some bacteria, yeasts and fungi are considered, as well as the recent advances in flavin biotechnology. The modern trends in microbial and enzymatic production of flavins are discussed.

Bacteria↗
PubMedDate not supplied

[The nature of the pyrimidine substrate of 6,7-dimethyl-8-ribityllumazine synthase participating in riboflavin biosynthesis in yeasts].

2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine and 2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine-5'-phosphate are studied for their effect on the activity of 6,7-dimethyl-8-ribityllumazine synthase of Pichia guilliermondii yeasts. It is shown that when nonphosphorylated form of pyrimidine and ribose-5-phosphate (donor C-4--a fragment) is used as a substrate, the specific activity of 6,7-dimethyl-8-ribityllumazine synthase is high and Be2+ and F- ions, inhibitors of alkaline phosphatases, do not inhibit it. The value of Km for this pyrimidine is 1.1 X 10(-5) M. Phosphorylated pyrimidine being used as a substrate in the presence of Be2+ and F-, the reaction practically does not proceed. Therefore, only 2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine is a pyrimidine substrate of 6,7-dimethyl-8-ribityllumazine synthase of yeast.

Multienzyme Complexes↗
PubMedDate not supplied

[Flavin biogenesis in yeasts].

The biosynthesis of flavins and methods for its study in yeast are considered. The chemical structure of flavin precursors and enzymes catalyzing certain stages of GTP transformation into riboflavin and flavin nucleotides are characterized. Differences in formation of flavins in bacteria and yeast are shown as well as possible ways of further research in this field.

Chemical Phenomena↗
PubMedDate not supplied

[Product of second-stage riboflavin biosynthesis in Pichia guilliermondii].

Dialyzed extracts of the mutants of Pichia guilliermondii RG80 (rib3, his-) and RA39 (rib3, ade-) in which the third step of flavinogenesis was genetically blocked converted GTP into 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine phosphate and 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine in the presence of NADPH2. Apparently, 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine phosphate is a true precursor of riboflavin whereas 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine is formed upon its hydrolysis.

Aminopyridines↗
PubMedDate not supplied

[Regulation of synthesis of GTP-cyclohydrolase participating in yeast falvinogenesis by iron].

Pichia guilliermondii, Schwanniomyces occidentalis, Torulopsis candida and several riboflavin-dependent mutants of Torulopsis candida were grown in a medium with a low concentration of iron. In these conditions, the activity of GTP-cyclohydrolase which catalyzes the first step of flavinogenesis increases. The activity of the enzyme increases also when the cells of T. candida and P. guilliermondii with a high content of iron are incubated with alpha, alpha'-dipyridyl which induces overproduction of riboflavin; this action of alpha, alpha'-dipyridyl is eliminated by cycloheximide. Therefore, iron deficiency in the cells of these yeasts causes derepression of GTP-cyclohydrolase participating in riboflavin biosynthesis. The activity of the enzyme is inhibited by FAD but not by FMN and riboflavin.

Aminohydrolases↗
PubMedDate not supplied

[GTP-cyclohydrolases of microorganisms and their role in metabolism].

The properties, regularities of biosynthesis and biochemical functions are considered of GTP-cyclohydrolases of microorganisms. The existence of two groups of these enzymes is established. The first group enzymes convert GTP into 7,8-dihydroneopterin-triphosphate and formiate. They participate in biosynthesis of tetrahydrofolic acid, tetrahydrobiopterin, molybdenic cofactor, pyrrolopyrimidine antibiotics and in a series of pigments. Representatives of the second group of cyclohydrolases convert GTP into 2,5-diamino-4-oxy-6-ribosylaminopyrimidine-5'-phosphate, formiate and pyrophosphate. They catalyze the first stages of formation of 6,7-dimethyl-8-ribityllumazine, flavins and their derivatives, toxoflavin (azapteridine antibiotics). The regulation of biosynthesis and activity of GTP-cyclohydrolases is studied only for individual enzymes of this group.

Aminohydrolases↗
PubMedDate not supplied

[Activity of the enzyme of the 2d step of flavinogenesis, 2,5-diamino-6-hydroxy-4-ribosylaminopyrimidine-5'-phosphate reductase, in Pichia guilliermondii yeasts].

The activity of 2,5-diamino-6-hydroxy-4-ribosylaminopyrimidine-5'-phosphate reductase, an enzyme of the second step of flavinogenesis, was studied in the yeast Pichia guilliermondii using a new fluorimetric technique. The activity of the enzyme was found in extracts of the wild-type strain and the genotype rib mutants but not in extracts of the FM 1-4 (rib 2) mutant. Interallelic complementation was revealed in the gene rib 2. The activity of the enzyme was identical in extracts of the cells grown in the medium with either a high or a low iron content which synthesized riboflavin at a low or a high rate, respectively. Therefore, the synthesis of this enzyme in P. guilliermondii is not regulated with iron.

Ascomycota↗