IRON REDUCTASE-ACTIVITY IN COWPEA RHIZOBIUM GN1 (PEANUT ISOLATE)

Cell-free extracts of cowpea Rhizobium GN1 (peanut isolate) possessed reductase activity towards various ferric siderophores including its o wn. This activity was heat- and O-2-sensitive and required NADH and fl avins. Whereas NADPH could replate NADH with half-efficiency, succinat e could not serve as reductant, Activity was insensitive to antimycin A and rotenone but was completely inhibited by HgCl2 (1 mM). Mg2+ (1 m M) enhanced reductase activity but Zn2+ and CU2+ at the same concentra tion were inhibitory. The enzyme was located in the periplasmic fracti on.