Journal of Lipid Research, Vol 23, 803-810, Copyright © 1982 by Lipid Research, Inc.
Effect of detergents on sterol synthesis in a cell-free system of yeast
S Hata, T Nishino, N Ariga and H Katsuki
In order to obtain information about the reactivity of enzymes in sterol
synthesis of yeast, the effects of some detergents were investigated. Among
the detergents used, Triton X-100 was found to exert a unique action, and
its effect on the incorporation of 14C- labeled acetate, mevalonate,
farnesyl pyrophosphate, or S-adenosyl-L- methionine into squalene,
2,3-oxidosqualene, and sterols in a cell-free system was examined. Triton
X-100 showed virtually no effect on the enzyme activities in the reactions
from acetyl CoA to farnesyl pyrophosphate, but it had a marked effect on
reactions from farnesyl pyrophosphate to ergosterol. Evidence was obtained
suggesting that Triton X-100 apparently activated squalene synthetase (EC
2.5.1.21) but inhibited squalene epoxidase (EC 1.14.99.7) and delta
24-sterol methyltransferase (EC 2.1.1.41). The activity of epoxidase was
protected from the inhibition by increasing the concentration of cell- free
extracts or by the prior addition of lecithin liposomes to the reaction
mixture. The inhibition of methyltransferase was partially reversed by
treatment with Bio-heads SM-2, but that of epoxidase was not reversed by
the treatment.
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