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.
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Research Article| April 15 1985
Kinetic studies with the low-Km aldehyde reductase from ox brain
Biochem J (1985) 227 (2): 621–627.
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C M Ryle, K F Tipton; Kinetic studies with the low-Km aldehyde reductase from ox brain. Biochem J 15 April 1985; 227 (2): 621–627. doi: https://doi.org/10.1042/bj2270621
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