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Purification and Properties of Nicotinamide Adenine Dinucleotide-Dependent D- and L-Lactate Dehydrogenases in a Group N Streptococcus

¹ Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria 3052, Australia, and C.S.I.R.O., Division of Food Research, Dairy Research Laboratory, Highett, Victoria 3190, Australia

ABSTRACT

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.