Purification and properties of nicotinamide adenine dinucleotide-dependent D- and L- lactate dehydrogenases in a group N streptococcus.

Streptococcus lactis strain 760, a group N streptococcus, was found to possess nicotinamide adenine dinucleotide-dependent dehydrogenase activities for both the l(+) and the d(-) isomers of lactic acid. The two enzymes were isolated and purified and were found to differ with respect to pH optima, activation by fructose-1,6-diphosphate, pH and heat stability, and the temperature at which each enzyme was formed in the organism during growth. The presence of a racemase for lactic acid was not detected by the methods used.