烟酸代谢。V. 钴胺素辅酶依赖性α-亚甲基戊二酸向二甲基马来酸的转化
Nicotinic acid metabolism. V. A cobamide coenzyme-dependent conversion of alpha-methyleneglutaric acid to dimethylmaleic acid.
作者信息
Kung H F, Cederbaum S, Tsai L, Stadtman T C
出版信息
Proc Natl Acad Sci U S A. 1970 Apr;65(4):978-84. doi: 10.1073/pnas.65.4.978.
A new B(12)-coenzyme-dependent isomerization, catalyzed by extracts of a nicotinate-fermenting clostridium, results in the conversion of alpha-methyleneglutaric acid to dimethylmaleic acid. These two acids are intermediates in the multistep anaerobic process wherein nicotinate is converted, ultimately, to one mole each of propionate, acetate, carbon dioxide, and ammonia. Dimethylmaleic acid reacts in its anhydride form with 2,4-dinitrophenylhydrazine to form N-2',4'-dinitrophenyl-anilino-3,4-dimethylmaleimide. The characteristic reddish color exhibited by the latter derivative in alkaline solution serves as a convenient quantitative assay for dimethylmaleic acid. Comparison of the 2,4-dinitrophenylhydrazine derivatives of the product of the enzymic reaction and of synthetic dimethylmaleic anhydride showed them to be identical in every respect.
由一种发酵烟酸的梭状芽孢杆菌提取物催化的一种新的依赖维生素B12的异构化反应，导致α-亚甲基戊二酸转化为二甲基马来酸。这两种酸是多步厌氧过程中的中间体，在该过程中，烟酸最终转化为一摩尔的丙酸、乙酸、二氧化碳和氨。二甲基马来酸以其酸酐形式与2,4-二硝基苯肼反应，形成N-2',4'-二硝基苯基-苯胺基-3,4-二甲基马来酰亚胺。后一种衍生物在碱性溶液中呈现的特征性红色可作为二甲基马来酸的便捷定量测定方法。酶促反应产物与合成二甲基马来酸酐的2,4-二硝基苯肼衍生物在各方面均显示相同。
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