title: Lactate dehydrogenase inhibitors in NADH preparations.
abstract: The presence of a new lactate dehydrogenase inhibitor on the trailing edge of the NADH peak from chromatography on diethylaminoethyl-celluose [Loshon et al., Clin. Chem., this issue] was verified. It was resolved from the NADH by high-performance liquid chromatography on muBondapak C18. When the new inhibitor was present in a reaction mixture to the extent that, of the initial 260-nm absorbance, about 5% was contributed by the inhibitor, the rate of NADH oxidation by lactate dehydrogenase decreased by 65%. The inhibitor absorbs at 260 and 340 nm, and is different from the Strandjord-Clayson inhibitor [J. Lab. Clin. Med. 67, 144 (1966)] by both types of chromatography. Because this new inhibitor has ultraviolet properties similar to those of NADH and chromatographs with the NADH on DEAE-cellulose, the high-performance liquid chromatographic method must be used to ensure its absence in preparations of NADH used for clinical assay.
mesh_terms: D002848:Chromatography, DEAE-Cellulose; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000302:isolation & purification*; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors*; D009243:NAD / Q000302:isolation & purification / Q000494:pharmacology*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004791:Enzyme Inhibitors; D009243:NAD; D007770:L-Lactate Dehydrogenase