Abstract

Reduction of cobalamin by non-dedicated cellular reductases has been reported in earlier work, however, the sources of reducing power and the mechanisms are unknown. This study reports results of kinetic and mechanistic investigation of the reaction between aquacobalamin, H₂OCbl, and reduced β-nicotinamide adenine dinucleotide, NADH. This interaction leads to the formation of one-electron reduced cobalamin, cob(II)alamin, and proceeds via water substitution on aquacobalamin by NADH and further decomposition of NADH–Co(III) complex to cob(II)alamin and NADH^·+. Riboflavin catalyzes the reduction of aquacobalamin by NADH both in free form and with aquacobalamin bound to the cobalamin processing enzyme CblC. The rate-determining step of this catalytic reaction is the interaction between riboflavin and NADH to produce a charge transfer complex that reacts with aquacobalamin. Aquacobalamin quenches the fluorescence of NADH and riboflavin predominantly via a static mechanism.

Graphic abstract

中文翻译：

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核黄素对电子从NADH转移到水钴胺的催化作用。

抽象的

在早期的工作中已经报道了通过非专用的细胞还原酶来还原钴胺素的方法，但是，还原能力的来源和机理尚不清楚。该研究报告了水钴胺，H ₂ OCbl和还原的β-烟酰胺腺嘌呤二核苷酸NADH之间反应的动力学和机理研究结果。这种相互作用导致单电子还原的钴胺素，cob（II）alamin的形成，并通过NADH在水钴胺素上进行水置换并进一步将NADH-Co（III）络合物分解为cob（II）alamin和NADH ^{· +来进行。}。核黄素以自由形式以及结合有钴胺素加工酶CblC的NADH催化NADH还原Aquacobalamin。该催化反应的决定速率的步骤是核黄素与NADH之间的相互作用，以产生与水钴胺素反应的电荷转移络合物。Aquacobalamin主要通过静态机制猝灭NADH和核黄素的荧光。

图形摘要