Ryder N S, Dupont M C
Biochim Biophys Acta. 1984 Jul 26;794(3):466-71. doi: 10.1016/0005-2760(84)90013-4.
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.
在致病性酵母白色念珠菌中研究了角鲨烯环氧酶的性质、要求以及一些抑制剂的作用。一个洗涤过的“微粒体”部分将放射性标记的角鲨烯转化为2,3-氧化角鲨烯和羊毛甾醇。活性的最低要求是分子氧、NADH或NADPH以及FAD。加入可溶性细胞质部分可使环氧酶活性提高达100%，而该部分本身的环氧酶活性可忽略不计。这种刺激在低酶浓度或高角鲨烯浓度时最为强烈。二价阳离子不刺激活性，EDTA也无抑制作用。在可溶性细胞质存在的情况下，确定角鲨烯的表观Km为50μM。环氧酶活性被 Triton X-100、脱氧胆酸盐或Cu2+破坏，并被硫醇试剂、鱼藤酮和抗霉素A部分抑制。该酶不受氰化物或几种细胞色素P-450抑制剂的抑制。
