BIOSYNTHESIS OF PORPHYRINS AND RELATED MACROCYCLES .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
BIOSYNTHESIS OF PORPHYRINS AND RELATED MACROCYCLES .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
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DOI：
10.1039/p19820002427
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发表时间：
1982-01-01
期刊：
影响因子：
--
通讯作者：
MATCHAM, GWJ
中科院分区：
文献类型：
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作者：
BATTERSBY, AR;FOOKES, CJR;MATCHAM, GWJ
当脱氨酶单独作用于胆色素原时，它会释放一种短暂的中间体到培养基中，该中间体不受用大量过量脱氨酶进一步处理的影响。该中间体经历快速的化学闭环（t1/2 [半衰期] apx. 4 min）以形成尿卟啉原-I。对由13 C标记的胆色素原产生的中间体的13 C光谱研究结合用于测定化学位移的标记标准品的合成，确定其结构为线性四吡咯，未重排的羟甲基胆烷。其他工作者推导出一种不同的环状结构，在这里通过化学研究，13 C光谱和13 C：15 N双标记实验证明是不正确的。该中间体是未重排的羟甲基胆烷，证实了其明确的合成。该bilane的天然和合成样品是用于产生uroporphyrinogen-III的辅助合成酶（不含脱氨酶）的优良和相同的底物。因此，脱氨酶是将4个胆色素原单元组装成线性四吡咯阶段的酶，而共合成酶是闭环和重排酶。两个建议进行了讨论的机制，在形成uropyrinogen-III的羟甲基胆烷的末端环-D的反转。
When the enzyme deaminase acts alone on porphobilinogen, it releases a transient intermediate into the medium which is unaffected by further treatment with a large excess of deaminase. The intermediate undergoes rapid ring-closure chemically (t1/2 [half-life] .apprx. 4 min) to form uroporphyrinogen-I. 13C Spectroscopic studies on the intermediate generated from 13C labeled porphobilinogen combined with synthesis of labeled standards for determination of chemical shifts establish its structure to be a linear tetrapyrrole, the unrearranged hydroxymethylbilane. Other workers deduced a different, cyclic structure which is shown here to be incorrect by chemical studies, 13C spectroscopy and 13C:15N double labeling experiments. That the intermediate is the unrearranged hydroxymethylbilane is confirmed by its unambiguous synthesis. The natural and synthetic samples of this bilane are excellent and identical substrates for cosynthetase (free from deaminase) with production of uroporphyrinogen-III. Thus, deaminase is the enzyme for assembly of 4 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 of uroporphyrinogen-III.