Solubilization and Properties of Formate Dehydrogenase and Cytochrome b1 from Escherichia coli*

Abstract

The particulate fraction (cf. S. Taniguchi and E. Itagaki, Biochim. Biophys. Acta, 44, 263(1960) was treated with crude snake venom (0.1%) at pH 8.0 in the presence of ethylenediamine tetraacetate (EDTA), the solubilized enzymes fractionated by (NH4)2SO4 (0.45 0.60 saturation), adsorbed on Ca3(PO4)2 gel at pH 7.1 and eluted with 0.2 M citrate buffer of pH 7.1. The preparation contained formate dehydrogenase (FD), cytochrome (cyt.) b1 and nitrate reductase (ND). FD was a metalloflavo-protein with essential SH-groups strongly but reversibly inhibited by O2. Cyt.-b1 was identified as a protoheme type readily autoxidizable. Reduction of cyt.-bi by FD-formate system required a lipid-sol. factor which could be replaced by vitamin-K3. Cyt.-b1 and methyl viologen could serve as an electron donor for the ND-nitrate system.