Identification of ergosterol and inhibition of sterol synthesis by. Delta. sup 5 -sterols in GL7, an auxotrophic mutant of yeast
Synthesis of ergosterol was demonstrated in the GL7 mutant of Saccharomyces cerevisiae. This sterol auxotroph has been thought to lack the ability to synthesize sterols due both to the absence of 2,3-oxidosqualene cyclase and to a heme deficiency eliminating cytochrome P-450 which is required in demethylation at C-14. However, when the exogenous sterol was 5{alpha}-cholestan-3{beta}-ol, 5{alpha}-cholest-8(14)-en-3{beta}-ol, or 24{beta}-methyl-5{alpha}-cholest-8(14)-en-3{beta}-ol, sterol synthesis was found to proceed yielding 1-3 fg/cell of ergosterol. Ergosterol was identified by mass spectroscopy, gas and high performance liquid chromatography, ultraviolet spectroscopy, and radioactive labelling from ({sup 3}H)acetate. Except for some cholest-5-en-3{beta}-ol (cholesterol) which was derived from the 5{alpha}-cholestan-3{beta}-ol, the stanol and the two 8(14)-stenols were not significantly metabolized confirming the absence of an isomerase for migration of the double bond from C-8(14) to C-7. Drastic reduction of ergosterol synthesis to not more than 0.06 fg/cell was observed when the exogenous sterol either had a double bond at C-5, as in the case of cholesterol, or could be metabolized to a sterol with such a bond. Thus, both 5{alpha}-cholest-8(9)-en-3{beta}-ol and 5{alpha}-cholest-7-en-3{beta}-ol (lathosterol) were converted to cholesta-5,7-dien-3{beta}-ol (7-dehydrocholesterol), and the presence of the latter dienol depressed the level of ergosterol.
- Research Organization:
- Drexel Univ., Philadelphia, PA (USA)
- OSTI ID:
- 5264038
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACETATES
BIOSYNTHESIS
CARBOXYLIC ACID SALTS
CHEMICAL BONDS
CHROMATOGRAPHY
CYCLASES
CYTOCHROMES
ENZYMES
ERGOSTEROL
EUMYCOTA
FUNGI
GAS CHROMATOGRAPHY
HYDROXY COMPOUNDS
INHIBITION
ISOTOPE APPLICATIONS
LIQUID COLUMN CHROMATOGRAPHY
LYASES
MASS SPECTROSCOPY
MICROORGANISMS
MUTANTS
ORGANIC COMPOUNDS
PIGMENTS
PLANTS
PROTEINS
SACCHAROMYCES
SACCHAROMYCES CEREVISIAE
SEPARATION PROCESSES
SPECTRA
SPECTROSCOPY
STEROIDS
STEROLS
SYNTHESIS
TRACER TECHNIQUES
ULTRAVIOLET SPECTRA
YEASTS