Kinetic studies with the low-Km aldehyde reductase from ox brain.
Initial-rate studies of the low-Km aldehyde reductase-catalysed reduction of pyridine-3-aldehyde by NADPH gave families of parallel double-reciprocal plots, consistent with a double-displacement mechanism being obeyed. Studies on the variation of the initial velocity with the concentration of a mixture of the two substrates were also consistent with a double-displacement mechanism. In contrast, the initial-rate data indicated that a sequential mechanism was followed when NADH was used as the coenzyme. Product-inhibition studies, however, indicated that a compulsory-order mechanism was followed in which NADPH bound before pyridine-3-aldehyde with a ternary complex being formed and the release of pyrid-3-ylcarbinol before NADP+. The apparently parallel double-reciprocal plots obtained in the initial-rate studies with NADPH and pyridine-3-aldehyde were thus attributed to the apparent dissociation constant for the binary complex between the enzyme and coenzyme being finite but very low.
D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D009540:Nicotinyl Alcohol / Q000494:pharmacology
D000447:Aldehydes; D009249:NADP; C014785:3-pyridinaldehyde; D009540:Nicotinyl Alcohol; D000429:Alcohol Oxidoreductases; C019642:alcohol dehydrogenase (NADP+)