烯丙胺与醌蛋白甲胺脱氢酶的反应机制
Mechanism of reaction of allylamine with the quinoprotein methylamine dehydrogenase.
作者信息
Davidson V L, Graichen M E, Jones L H
机构信息
Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216-4505, USA.
出版信息
Biochem J. 1995 Jun 1;308 ( Pt 2)(Pt 2):487-92. doi: 10.1042/bj3080487.
Allylamine did not serve as an efficient substrate for methylamine dehydrogenase (EC 1.4.99.3) in a steady-state assay of activity and appeared to act as a competitive inhibitor of methylamine oxidation by methylamine dehydrogenase. Transient kinetic studies, however, revealed that allylamine rapidly reduced the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase. The rate of TTQ reduction by allylamine was 322 s-1, slightly faster than the rate of reduction by methylamine. These data were explained by a kinetic mechanism in which allylamine and methylamine are alternative substrates for methylamine dehydrogenase. The apparent competitive inhibition by allylamine is due to a very slow rate of release of the aldehyde product, 0.28 s-1, relative to a rate of 18.6 s-1 for the release of the aldehyde product of methylamine oxidation. A reaction mechanism is proposed for the oxidative deamination of allylamine by methylamine dehydrogenase. This mechanism is discussed in relation to the reaction mechanisms of topa-bearing quinoprotein amine oxidases, the flavoprotein monoamine oxidase and the mammalian semicarbazide-sensitive amine oxidase.
在稳态活性测定中，烯丙胺并非甲胺脱氢酶（EC 1.4.99.3）的有效底物，且似乎对甲胺脱氢酶氧化甲胺起到竞争性抑制作用。然而，瞬态动力学研究表明，烯丙胺能迅速还原甲胺脱氢酶的色氨酸-色氨酸醌（TTQ）辅因子。烯丙胺还原TTQ的速率为322 s⁻¹，略快于甲胺的还原速率。这些数据可用一种动力学机制来解释，即烯丙胺和甲胺是甲胺脱氢酶的替代底物。烯丙胺明显的竞争性抑制作用是由于醛产物的释放速率非常缓慢，为0.28 s⁻¹，而甲胺氧化的醛产物释放速率为18.6 s⁻¹。本文提出了甲胺脱氢酶氧化脱氨烯丙胺的反应机制。该机制与含topa醌蛋白胺氧化酶、黄素蛋白单胺氧化酶和哺乳动物氨基脲敏感胺氧化酶的反应机制相关进行了讨论。
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