Effects of various inhibitors on desaturase and reductase enzyme activities in Tetrahymena microsomal electron transport system

Abstract

1. 1. The effects of several inhibitors on the Tetrahymena microsomal desaturase and cytochrome reductase activity were studied. 2. 2. Cyanide strongly inhibited Tetrahymena microsomal desaturation supported by either NADH or NADPH. Moreover, NADH- and NADPH-dependent desaturase activity was inhibited by cytochrome c and ferricyanide which are artificial electron acceptors. 2′-AMP, a competitive inhibitor versus NADPH, inhibited NADPH-dependent desaturation, while NADH-desaturase activity was not affected by this nucleotide. 3. 3. NADH-ferricyanide and NADPH-cytochrome c reductase activities as well as microsomal desaturase activity were sensitive to p-chloromercuribenzoate, mercuric chloride and N-ethylmaleimide respectively. This indicated that the sulfhydryl groups of NADH-ferricyanide reductase and NADPH-cytochrome c reductase are essential for the interaction of nucleotides with these flavoproteins in Tetrahymena microsomes.