Biosynthesis of porphyries and related macrocycles. Part 18. Proof by spectroscopy and synthesis that unrearranged hydroxymethylbilane is the product from deaminase and the substrate for cosynthetase in the biosynthesis of uroporphyrinogen-III
作者:Alan R. Battersby、Christopher J. R. Fookes、Kerstin E. Gustafson-Potter、Edward McDonald、George W. J. Matcham
DOI:10.1039/p19820002427
日期:——
excellent and identical substrates for cosynthetase (free from deaminase) with production of uroporphyrinogen-III. Thus, deaminase is the enzyme for assembly of four porphobilinogen units to the linear tetrapyrrole stage and cosynthetase is the ring-closing and rearranging enzyme. Two proposals are discussed for the mechanism of inversion of the terminal ring-D of the hydroxymethylbilane in the formation
当脱氨酶单独作用于胆色素原时,它会向培养基中释放出一种短暂的中间体,该中间体不受大量脱氨酶的进一步处理的影响。中间经历快速ringclosure化学(吨½约4分钟),以形成尿卟啉原-I。对13 C标记的胆色素原生成的中间体进行13 C光谱研究,并结合用于测定化学位移的标记标准品,确定其结构为线性四吡咯,即未重排的羟甲基胆烷。其他工人推论出不同的循环结构(前尿素),根据化学研究,13 C光谱和13证明,此处是不正确的C:15 N双标记实验。通过其明确的合成证实了该中间体是未重排的羟甲基胆烷。该胆烷的天然和合成样品显示是极好的,并且与合成蛋白(不含脱氨酶)具有相同的底物,可生产尿卟啉原-III。因此,脱氨酶是用于将四个胆色素原单元组装到线性四吡咯阶段的酶,而辅酶是闭环和重排的酶。讨论了关于在尿卟啉原-III形成过程中羟甲基bilane的末端环-D转化机理的两个建议。