Koudelka A P, Kambadur N, Bradley D K, Ferguson K A
Biochim Biophys Acta. 1983 Mar 22;751(1):121-6. doi: 10.1016/0005-2760(83)90263-1.
Tetrahymena microsomes contain cytochrome b5 and an NADH-dependent cytochrome b5 reductase, but these proteins are present at only one-tenth the levels observed in rat liver microsomes. We show that both proteins can be partially purified by techniques developed for the rat liver proteins. We can show that cyanide inhibits the rate of exhaustion of NADH, and therefore reoxidation of cytochrome b5 by microsomes, and that stearoyl CoA enhances the rate of reoxidation of the cytochrome. Also, we find that a fragment of rat liver NADH-cytochrome b5 reductase can restore NADH-dependent cytochrome b5 reduction to Tetrahymena microsomes which have been treated with N-ethylmaleimide to eliminate endogenous reductase activity. These results indicate that there is considerable resemblance between the rat and Tetrahymena systems, and that desaturation of stearoyl and oleoyl groups may occur in Tetrahymena via pathways similar to those known in liver.
四膜虫微粒体含有细胞色素b5和一种依赖NADH的细胞色素b5还原酶，但这些蛋白质的含量仅为大鼠肝脏微粒体中观察到水平的十分之一。我们表明，这两种蛋白质都可以通过为大鼠肝脏蛋白质开发的技术进行部分纯化。我们可以证明，氰化物会抑制NADH的消耗速率，从而抑制微粒体对细胞色素b5的再氧化，而硬脂酰辅酶A会提高细胞色素的再氧化速率。此外，我们发现大鼠肝脏NADH-细胞色素b5还原酶的一个片段可以将依赖NADH的细胞色素b5还原恢复到经N-乙基马来酰亚胺处理以消除内源性还原酶活性的四膜虫微粒体中。这些结果表明，大鼠和四膜虫系统之间存在相当大的相似性，并且硬脂酰和油酰基团的去饱和可能在四膜虫中通过与肝脏中已知途径相似的途径发生。
