Physiological Effects of an Antimycotic Azasterol on Cultures of Saccharomyces cerevisiae

mentioning

confidence: 98%

mentioning

confidence: 99%

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Self-induced nystatin resistance in Dictyostelium discoideum

Kasbekar¹,

Madigan²,

Katz³

1985

“…We have presented studies on another compound, 15-aza-24-methylene-8,14-cholestadien- 33-ol (15-azasterol), with strong antifungal activity (13,14,23). This compound inhibits a step in C-14 demethylation (4) which leads to the accumulation of A8,14-ergostadien-3,3-ol (ignosterol).…”

mentioning

confidence: 99%

Relationship between antifungal activity and inhibition of sterol biosynthesis in miconazole, clotrimazole, and 15-azasterol

Taylor¹,

Rodriguez²,

Parks³

1983

The availability of Saccharomyces cerevisiae mutants which are defective in sterol biosynthesis makes it possible to determine whether the ability of several antifungal agents to inhibit cell growth is due to their effect on sterol production. 15-Aza-24-methylene-8,14-cholestadien-3 beta-ol (15-azasterol) is known to block the reduction of the sterol delta 14 bond following C-14 demethylation. This agent inhibits the growth of wild-type S. cerevisiae but does not inhibit the growth of a strain that is defective in the removal of the C-14 methyl group of lanosterol and in the introduction of the 5,6 double bond. 15-Azasterol does not inhibit the growth of a sterol auxotrophic strain growing on an exogenous supply of sterol. Therefore, the effect of 15-azasterol on sterol biosynthesis is clearly the cause of its ability to inhibit growth. On the other hand, growth inhibition by two imidazole antifungal agents, clotrimazole and miconazole, cannot be ascribed to their ability to prevent the removal of the C-14 methyl group of lanosterol, because they inhibit the growth of the sterol auxotrophic strain as well as that of the demethylase mutant.

“…When S. cerevisiae is exposed to picomolar concentrations of 15-azasterol, variations in the normal cellular sterol pool can be observed (5). Although no major deviation in cell growth is seen at such low concentrations, the yeast synthesizes ergosta-8,14-3,B-ol (ignosterol) rather than ergosta-5,7,22-trien-3,8-ol (ergosterol), the major sterol normally found in yeasts (6).…”

mentioning

confidence: 99%

Growth and antifungal homoazasterol production in Geotrichum flavo-brunneum

Rodríguez¹,

Parks²

1980

The growth cycle and production of 15-aza-24-methylene-8,14-cholestadiene3f8-ol (15-azasterol) in Geotrichum flavo-brunneum strain NRRL28804 have been studied. During the growth cycle of this organism, morphological changes were noted which corresponded to changes in the pH of the culture medium. A physiological shift from acid to base production also occurred during the growth cycle. Concomitant When S. cerevisiae is exposed to picomolar concentrations of 15-azasterol, variations in the normal cellular sterol pool can be observed (5). Although no major deviation in cell growth is seen at such low concentrations, the yeast synthesizes ergosta-8,14-3,B-ol (ignosterol) rather than ergosta-5,7,22-trien-3,8-ol (ergosterol), the major sterol normally found in yeasts (6). Inhibition by 15-azasterol has been demonstrated on three enzymes of the sterol pathway in S. cerevisiae: A24-sterol methyltransferase (1), 24-methylene sterol A24 (28) Berkeley, was also used. In most experiments, cells were cultured in liquid medium containing 1% tryptone and 0.5% yeast extract with 2% glucose as the carbon source. In experiments to determine the effect of pH on growth, cells were also grown in liquid medium containing yeast nitrogen base (Difco Laboratories) with 2% glucose as the carbon source. Growth of NRRL28804 was measured by the change in dry weight per volume of culture medium. All experiments were conducted at 28°C, and cells were grown aerobically with reciprocal shaking.Mixed culture analysis. Log-phase NRRL28804 cells were combined with log-phase A364a cells in an equal cellular ratio. To determine the change in relative cell number with time, samples were taken periodically and cells were differentiated and enumerated with an American Optical hemacytometer.Determination of an optimal medium for production of inhibitory factor. Optimal conditions were determined by growing NRRL28804 in various media and extracting both the cells and media for the inhibitory factor. Cells were grown in 100 ml of liquid media containing different carbon sources. After 5 days of growth, the cells were harvested by centrifugation at 500 x g for 10 min. The cell pellets were suspended in 25 ml of chloroform and incubated overnight at 4°C. Chloroform extracts were filtered to remove debris and concentrated to 5 ml on a Brinkman rotating evaporator operated at 30°C. The 100-ml medium samples were extracted with 50 ml of chloroform and processed in the same manner.Inhibition by the various extracts was determined by the standard disk method. Antibiotic paper disks were wetted with 25 pd of each extract and allowed to dry for 4 h at room temperature. A lawn containing approximately 106 cells of A364a in the log phase of growth was spread on the tryptone-yeast-glucose medium described above, and the dried disks were immediately placed on top of the yeast cells.