[Biochemical basis of varying nystatin resistance of Saccharomyces cerevisiae and Candida maltosa mutants].

Six groups of nystatin resistant mutants of C. maltosa and of haploid and diploid Saccharomyces cerevisiae strains were obtained with the help of genetic and biochemical analysis. It has been shown that every group of the mutants was characterized by a specific level of resistance to nystatin.

[Sterol level in Saccharomyces cerevisiae mutants with altered ergosterol biosynthesis].

The sterol content in Saccharomyces cerevisiae mutants defective in the synthesis of cyclic ergosterol precursors has been studied. It was found that strains with mutational blocks involving the stages of zymosterol side chain methylation at C24 and delta 8----delta 7 isomerization accumulated twice more sterols as compared to parent strains. Regulation of the ergosterol biosynthesis is discussed.

[The use of various mutagens for induction of nystatin-resistant mutants in Candida maltosa].

The mutagenic activity of nitrous acid, 6-N-hydroxylaminopurine, N-methyl-N'-nitro-N-nitrosoguanidine and 4-N-nitroquinoline oxide was studied for Candida maltosa. The efficacy of their action on C. maltosa cells was determinded in order to obtain nystatin-resistant strains.

[The level of cytochrome P-450 in Saccharomyces cerevisiae with disruptions of various stages of sterol synthesis].

A spectral analysis of cytochromes P-450 in Saccharomyces cerevisiae cells and in mutant strains accumulating the ergosterol biosynthesis intermediates was carried out. Glucose repression and semianaerobiosis were found to induce cytochrome P-450 synthesis. No differences in the cytochrome P-450 content in mutant nys 3, nys 4 and parent strains were observed.

[Substrate specificity of the biotransformation enzymes in a Nocardia erythropolis culture].

Substrate specificity of biotransformation enzymes of culture Nocardia erythropolis was studied. Products of transformation of cholesterol and three sterols of microbial origin: ergosterol, ergosta-5,7-dien-3 beta-ol and ergosta-7,22-dien-3 beta-ol was identified with a help of thin-layer chromatography, UV spectrophotometry and mass-spectrometry. It was established, that delta 22-bond in the side chains of sterols and delta 7-bond slows and delta 5-bond makes impossible cleavage of side chains of sterols.

[Oleandomycin and its natural and synthetic analogs. II. Structure and properties of oleandomycin B, a new compound of the oleandomycin group].

The revealed regularities of mass spectroscopic disintegration of oleandomycin and its derivatives made it possible to determine analytic criteria for identification of compounds related by their structure to oleandomycin. Analysis of the extracts from oleandomycin fermentation broth filtrates on the basis of the selected group of diagnostic ions showed that along with the main antibiotic there formed during the biosynthesis oleandomycin B, a structurally close minor component. The structure of the substance was assigned and its physico-chemical and biological properties were studied.

[Oleandomycin and its natural and synthetic analogs. I. Dissociative ionization of oleandomycin and its derivatives].

Regularities of dissociative ionization of compounds belonging to the oleandomycin group were studied. Mass spectra of oleandomycin and some of its derivatives including anhydrooleandomycin, oleandomycin chlorhydrine, desoleandomycin, oleandomycin oxide, trimethylsilyl and acetyl derivatives were analyzed comparatively. Directions of disintegration with breakage of the glycoside bonds, macrolactone and carbon cycles were detected.

[The effect of oxygen deficiency on the stability of the yeast Saccharomyces cerevisiae to the polyenic antibiotic nystatin].

Oxygen deficiency was shown to affect the resistance of different Saccharomyces cerevisiae strains to nystatin, a polyenic antibiotic. This resistance decreased upon oxygen deficiency in the wild-type strains alpha'1 and 7A-P192 as well as in the mutant strains NYS 2, NYS 3 and NYS 4, but remained unchanged in the mutants NYS-1 and NYS 5. The qualitative composition of sterols was studied in the strains with a modified ergosterol synthesis, which were grown under the conditions of oxygen deficiency.

[Characteristics of the final stages of ergosterol biosynthesis in Saccharomyces cerevisiae yeasts].

A scheme of ergosterol cyclic intermediate transformations in S. cerevisiae has been proposed. It is based on the analysis of sterol composition in strains with mutant blocks of one or two reactions of enzymatic synthesis.

[Analysis of the products of ergosta-7,22-dien-3-beta-ol biotransformation by a Nocardia erythropolis culture].

The products of biotransformation by Nocardia erythropolis-402 of the microbial sterol ergosta-7,22-dien-3 beta-ol isolated from a Saccharomyces cerevisiae mutant were studied. The products were identified as ergosta-7,22-dien-3-one and ergosta-7,22-dien-17 alpha-ol-3-one by thin-layer chromatography, UV-spectrophotometry and mass-spectroscopy. It was found that the existence of 7-8 double bond slowed down the cleavage of the sterol side chain.

[Yeast resistance to polyene antibiotics. VII. The interaction of the mutant alleles of the nystatin resistance genes in Saccharomyces cerevisiae].

The data on allele interactions of nystatin resistance genes are presented. It has been shown that the mutant phenotype of heteroallelic hybrids NYS1, NYS4 and, probably, NYS3 is strengthened. The intragenic complementation has been found in NYS2 gene, allowing to imply the multimeric structure of delta 8----delta 7 isomerase which is controlled by this gene.

[Evaluation of the vitamin D activity of yeasts with altered sterol metabolism].

The sterol content of Saccharomyces strains with altered ergosterol metabolism was studied by UV-spectrophotometry, thin-layer chromatography and chromatographic mass-spectroscopy. A technique for estimation of D-vitamin activity of the yeast strains is proposed. The irradiated biomass of the strains accumulated ergosta-5,7-dien-3 beta-ol and also cholesta-5,7,24-trien-3 beta-ol and cholesta-5,7,22,24-tetraen-3 beta-ol is characterized by high antirachitic activity.

[Yeast resistance to polyene antibiotics. VI. Isolation and biochemical analysis of strains of Saccharomyces cerevisiae yeasts with mutations in the 2 nystatin-resistance genes].

The comparative analysis of sterol content in the yeast Saccharomyces cerevisiae strains singly or doubly defective in nystatin resistance genes was carried out. The strains with two mutations in NYS genes were shown to accumulate the sterol mixture, similar to that of the parental singly defective mutant. This type of gene interaction allows to define the main biochemical order of reaction in ergosterol synthesis: methylation in C24 (NYS1), delta 8----delta 7 isomerization (NYS2), C5 (6) and C22 (23) desaturation (NYS3 and NYSX).

[A method of determining the level of provitamin D in Saccharomyces cerevisiae with altered sterol metabolism].

A method is proposed that allows to choose among the polyene-resistant mutants of the yeasts Saccharomyces cerevisiae with changed biosynthesis of ergosterol promising producers of provitamin D4 and structural analogs of provitamin D3. The method involves both UV-spectrophotometry and thin-layer chromatography. The results obtained are supported by the data of mass-spectrometry of sterols.

[A method of quantitative determination of delta 5,7-sterols in unsaponifiable lipid fractions].

The technique is offer for rapid quantitative definition of sterols having a system of delta 5,7-conjugated double bonds which conditions biological activity of D vitamin--the result of photoisomerisation of the sterols. The technique bases on the analysis of UV absorption spectra of unsaponifiable lipid fraction of several kinds of mutant yeast strains and the model mixtures of sterols. The results obtained concerning the estimation of delta 5,7-sterols containing in total fraction are confirmed by gas-liquid-chromatography and mass-spectrometry data.

[Sterol composition in yeast strains sensitive and resistant to nystatin].

The sterol composition of nystatin-sensitive and nystatin-resistant strains of Saccharomyces cerevisiae was being studied by gas-liquid chromatography and mass-spectroscopy. The synthesis of ergosterol is completely suppressed in polyene-resistant mutants. Three sterols derived from cholesterol were identified in the mutants: cholesta-8,24-diene-3 beta-ol, cholesta-5,7,24-triene-3 beta-ol, and cholesta-5,7,22,24-tetraene-3 beta-ol.