Effect of detergents on sterol synthesis in a cell-free system of yeast

Nucleotide sequence of a cDNA for mouse squalene epoxidase

A full-length cDNA encoding mouse squalene epoxidase was isolated by screening a mouse liver cDNA library with the rat squalene epoxidase gene as a probe. The cDNA had an open reading frame for a 572 amino acid polypeptide with a calculated molecular mass of 63.8 kDa. The predicted amino acid sequence of the mouse enzyme contained an FAD-binding motif, and was 93% identical to that of the rat enzyme. The former is one amino acid shorter than the latter. Blotting analyses showed that the mRNA is 2.8 kb in size and that a single copy of the gene is present in the mouse genome.

Properties of a particulate squalene epoxidase from Candida albicans

The properties and requirements of squalene epoxidase and effects of some inhibitors were investigated in the pathogenic yeast Candida albicans. A washed 'microsomal' fraction converted radiolabelled squalene to 2,3-oxidosqualene and lanosterol. Minimum requirements for activity were molecular oxygen, NADH or NADPH, and FAD. Epoxidase activity was stimulated by up to 100% by addition of the soluble cytoplasmic fraction, which itself contained negligible epoxidase activity. This stimulation was most powerful at low concentrations of enzyme, or high concentrations of squalene. Divalent cations did not stimulate activity and EDTA was not inhibitory. An apparent Km for squalene of 50 microM was determined in the presence of soluble cytoplasm. Epoxidase activity was destroyed by Triton X-100, deoxycholate or Cu2+, and partially inhibited by thiol reagents, rotenone and antimycin A. The enzyme was not inhibited by cyanide or by several inhibitors of cytochrome P-450.

Androgenic control of acetate incorporation into phospholipids and triacylglycerols in rat ventral prostate

To obtain information about androgenic hormone actions on the synthesis of lipids from [1-14C]acetate in rat ventral prostate, in vitro and in vivo experiments have been carried out. The time course of incorporation of labelled acetate was studied. Also different solubilization media of androgenic hormones was investigated. We have selected Tween-80. Results for in vitro experiments, show that increasing concentrations of testosterone and dihydro-testosterone correspond to an increase in the incorporation of labelled acetate into phospholipids and a decrease in the incorporation into triacylglycerols. In vivo experiments of incorporation of [1-14C]acetate have also been carried out and show a similar pattern to the situation found in our in vitro experiments.