Intact mycelia from wild-type Phycomyces blakesleeanus NRRL 1555(-) are capable to reduce the rate of chemical oxidation of extracellular ascorbate. Plasma membrane isolated from this fungus catalysed NADH oxidation using ferricyanide and ascorbate free radical (AFR) in a ratio of specific activities of 40:1. NADH-AFR reductase activity was stimulated by CoQ6 and inhibited by chloroquine, the inhibition being partially reversed by CoQ6. However, ferricyanide reductase activity was insensitive to both effectors. In addition, the extraction of CoQ from plasma membrane resulted in a lack of NADH-AFR reductase activity; addition of extra CoQ6 to these extracted membranes restored about 85% the original activity. Ferricyanide reductase activity was unaffected under similar experimental conditions. NADH-AFR reductase activity can also be differentiated from ferricyanide reductase activity by its sensitivity to detergents: CHAPS and Triton X-100 inhibited AFR reductase, but have not effect on ferricyanide reductase activity. These results indicate that NADH-AFR reductase activity is a different enzymatic activity of previously described ferricyanide reductase activity, as well as the participation of CoQ in the AFR reduction by NADH-AFR reductase activity from Phycomyces blakesleeanus plasma membrane.
Buy this Article