Novel sterols in ergosterol deficient yeast mutants

AnUstilago maydisMutant Partially Blocked in P45014DMActivity Is Hypersensitive to Azole Fungicides

“…Planarity of the sterol ␣-face is thought to be necessary for correct packing of the sterol molecule between fatty acyl groups of membrane phospholipids (Vanden Bossche, 1990). In recent years, P450 14DM has attracted a great deal of attention because it is the established target site for a number of commercially important fungicides and antimycotic drugs (azoles, purines, and pyrimidines) collectively termed demethylase inhibitors or DMIs 2 (Köller, 1992) Despite the effectiveness of DMIs in controlling the growth of fungal diseases, viable mutants deficient in P450 14DM activity have been recovered from the yeasts Saccharomyces cerevisiae (Taylor et al, 1983;Trocha et al, 1974) and Candida albicans (Bard et. al., 1987;Pierce et al, 1978), and from the basidiomycete plant pathogenic fungus Ustilago maydis (James et al, 1992;Walsh and Sisler, 1982).…”

Mechanism of action of Denmert, an inhibitor of sterol biosynthesis

“…In their mutants, 14C-acetate incorporation into the 4-desmethyl sterol fraction was markedly reduced and the radioactivity tended to accumulate in the fractions of squalene, 4,4-dimethyl sterols and 4~-methyl sterols. Identification of sterols obtained from nystatin-resistant and ergosterol-requiring mutants of yeast was conducted by Trocha et al (1974). The mutants were found to contain 14~-methyl fecosterol, lanosterol, obtusifoliol, and 4,14-dimethyl zymosterol.…”

Cytochrome P450 of Fungi: Primary Target for Azole Antifungal Agents

“…Recently, Yoshida et al (lIS, 119) purified a cytochrome P450 (P450 sGl ) from a nystatin-resistant mutant, S. cerevisiae SG 1, which was defective in lanosterol14cx-demethylation (10,94,95). P450 sG1 is immunochemically the same protein as P450 14DM , and peptide maps of P450 sG1 are superimposable on those ofP450 14DM (10,119).…”

“…We also found that rabbit antibodies to P450 14DM of S. cerevisiae (12) inhibited the demethylase activity of some yeasts, although the inhibition was weaker than that observed with S. cerevisiae microsomes (Aoyama Y, and Yoshida Y, unpublished results). Furthermore there are many studies (16,41,49,62,79,92,99) describing accumulation of 14-methylsterols in pathogenic fungi treated with antifungal agents known to inhibit P450 14DM • However, no attempt has been made to isolate and characterize the P450 14DM • The initial step oflanosterol metabolism in yeasts is the l4cx-demethylation by P45014DM• A large amount of the sterol is known to accumulate in a mutant yeast, S. cerevisiae SGI (94,95), which is defective in P450 14DM (10). In contrast, there are some studies (16,41,49,62,92,99,101) describing the observation that many fungi treated with an antifungal agent known to inhibit P450 14DM will result in the accumulation of 24-methylene-24,25-dihydrolanosterol rather than lanosterol.…”