title: Effect of reaction initiator on human lactate dehydrogenase assay.
abstract: Human lactate dehydrogenase isoenzymes I and V have decreased activities when the reaction is initiated with lactate. No loss in lactate dehydrogenase I activity was found when the reaction was initiated with enzyme or NAD+. For lactate dehydrogenase V an NAD+-initiated reaction, as compared to an enzyme-initiated reaction, yields lower activity in sodium pyrophosphate buffer but higher activity in tris(hydroxymethyl)aminomethane buffer. Both isoenzymes have higher lactate-to-pyruvate activity when assayed in the latter buffer than when assayed in the former. Human lactate dehydrogenase V (but not I) exhibited different activities when assayed with lactate from two different commercial sources. Human lactate dehydrogenase assayed by the pyruvate-to-lactate reaction is not affected by the choice of reaction initiator.
mesh_terms: D006801:Humans; D007527:Isoenzymes; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000097:blood* / Q000378:metabolism; D007773:Lactates / Q000494:pharmacology; D008722:Methods; D009243:NAD / Q000494:pharmacology*
chemical_list: D007527:Isoenzymes; D007773:Lactates; D009243:NAD; D007770:L-Lactate Dehydrogenase