The isolation and some properties of the membrane-bound lactate dehydrogenase of Paracoccus denitrificans

Membrane-bound lactate dehydrogenase was isolated from the cells of Paracoccus denitrificans by a combination of phase separation and chromatographic methods. It was NAD(+)-independent; phenazine methosulphate and 2,6-dichlorophenolindophenol could act as electron accepters. It preferred D-lactate over the L-form (K-m = 0.81 and 4.40 mM, respectively). Relative molecular weight estimations were 54 000 +/- 3 000 (electrophoresis) and 50 000 +/- 5 000 (gel chromatography). It was inhibited by thenoyltrifluoroacetone and diethyl pyrocarbonate, SH-reagents were 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.