Also oxidizes other (S)-2-hydroxy-monocarboxylic acids. NADP+ also acts, more slowly, with the animal, but not the bacterial, enzyme.

L-lactate dehydrogenase catalyzes the reversible NAD-dependent interconversion of pyruvate to L-lactate. In vertebrate muscles and in lactic acid bacteria it represents the final step in anaerobic glycolysis. This tetrameric enzyme is present in prokaryotic and eukaryotic organisms. In vertebrates there are three isozymes of LDH: the M form (LDH-A), found predominantly in muscle tissues; the H form (LDH-B), found in heart muscle and the X form (LDH-C), found only in the spermatozoa of mammals and birds. In birds and crocodilian eye lenses, LDH-B serves as a structural protein and is known as epsilon-crystallin.

As a signature for LDH's it was selected a region that includes a conserved histidine which is essential to the catalytic mechanism.
Reference