Bognar A, Meighen E
Can J Biochem Cell Biol. 1983 May;61(5):301-6. doi: 10.1139/o83-041.
The kinetic mechanism of a long-chain aldehyde dehydrogenase that is induced during the development of bioluminescence in Beneckea harveyi has been investigated. Parallel lines were obtained in Lineweaver-Burk plots with NAD+ and long-chain aldehydes (heptaldehyde, nonylaldehyde). However, product and dead-end inhibitor studies, substrate protection (NAD+, aldehyde) against inactivation with N-ethylmaleimide, and in particular, a noncompetitive substrate inhibition pattern with aldehyde at high concentrations showed that aldehyde dehydrogenase had a sequential mechanism. The data were consistent with a nonrapid equilibrium random mechanism with a preferred order of addition of substrates (NAD+, aldehyde) and an ordered release of products with NADH release being the last and rate-limiting step in the reaction, a mechanism very similar to that found for short-chain mammalian aldehyde dehydrogenases. The present experiments emphasize the caution that must be taken in interpreting parallel patterns in initial velocity experiments, as well as the difficulty in classifying sequential enzyme mechanisms as either strictly ordered or random.
对哈维氏贝内克氏菌生物发光发育过程中诱导产生的一种长链醛脱氢酶的动力学机制进行了研究。在双倒数图中，使用NAD⁺和长链醛（庚醛、壬醛）得到了平行直线。然而，产物和终产物抑制剂研究、底物（NAD⁺、醛）对N - 乙基马来酰亚胺失活的保护作用，特别是高浓度醛时醛脱氢酶呈现的非竞争性底物抑制模式表明，醛脱氢酶具有有序机制。数据与非快速平衡随机机制一致，底物（NAD⁺、醛）优先按特定顺序添加，产物按有序方式释放，其中NADH的释放是反应的最后一步且为限速步骤，该机制与短链哺乳动物醛脱氢酶的机制非常相似。本实验强调了在解释初速度实验中的平行模式时必须谨慎，以及将有序酶机制严格分类为严格有序或随机机制的困难。
