METHYL TRANSFER FROM METHYLCOBALAMIN TO THIOLS - A REINVESTIGATION
METHYL TRANSFER FROM METHYLCOBALAMIN TO THIOLS - A REINVESTIGATION
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DOI：
10.1021/bi00344a018
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发表时间：
1985-01-01
期刊：
影响因子：
2.9
通讯作者：
SUN, S
中科院分区：
文献类型：
--
作者：
HOGENKAMP, HPC;BRATT, GT;SUN, S
从甲钴胺到硫醇的甲基转移已被重新研究。通过使用在甲基部分选择性富集 13C 的甲钴胺，通过 13C NMR 跟踪甲基向硫醇的转移。即使在完全没有氧气的情况下，甲基转移也会在弱碱性（pH 8-12）水溶液中发生。 31P NMR 和 EPR 研究表明 cob(II)alamin 是最终的类咕啉产物。然而，从甲基钴胺素到β-巯基乙醇的甲基转移反应的pH依赖性仅与硫醇根阴离子对甲基的亲核置换一致，导致碳-钴键的异裂。反应混合物的差异可见光谱测量表明钴(I)丙胺作为中间体形成。
The methyl transfer from methylcobalamin to thiols has been reinvestigated. By use of methylcobalamin selectively enriched with 13C in the methyl moiety, the methyl transfer to thiols was followed by 13C NMR. The methyl transfer occurs in aqueous mildly alkaline (pH 8-12) solution, even in the complete absence of oxygen. 31P NMR and EPR studies demonstrate that cob(II)alamin is the final corrinoid product. However, the pH dependence of the methyl-transfer reaction from methylcobalamin to .beta.-mercaptoethanol is consistent only with a nucleophilic displacement of the methyl group by a thiolate anion, resulting in the heterolytic cleavage of the carbon-cobalt bond. Difference visible spectroscopic measurements of the reaction mixture suggest that cob(I)alamin is formed as an intermediate.