THE ISOLATION AND SOME PROPERTIES OF THE MEMBRANE-BOUND LACTATE-DEHYDROGENASE OF PARACOCCUS-DENITRIFICANS

Membrane-bound lactate dehydrogenase was isolated from the cells of Pa racoccus denitrificans by a combination of phase separation and chroma tographic methods. It was NAD(+)-independent; phenazine methosulphate and 2,6-dichlorophenolindophenol could act as electron accepters. It p referred D-lactate over the L-form (K-m = 0.81 and 4.40 mM, respective ly). Relative molecular weight estimations were 54 000 +/- 3 000 (elec trophoresis) and 50 000 +/- 5 000 (gel chromatography). It was inhibit ed by thenoyltrifluoroacetone and diethyl pyrocarbonate, SH-reagents w ere without effect. No other lactate dehydrogenase activity was found in any subcellular fraction of cells grown on D,L-lactate, L-lactate, glucose or succinate.