MECHANISM AND STEREOCHEMISTRY OF ENZYMIC REACTIONS INVOLVED IN PORPHYRIN BIOSYNTHESIS
MECHANISM AND STEREOCHEMISTRY OF ENZYMIC REACTIONS INVOLVED IN PORPHYRIN BIOSYNTHESIS
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DOI：
10.1098/rstb.1976.0005
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发表时间：
1976-01-01
期刊：
影响因子：
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通讯作者：
ZAMAN, Z
中科院分区：
文献类型：
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作者：
AKHTAR, M;ABBOUD, MM;ZAMAN, Z
5-氨基乙酰丙酸合成酶催化甘氨酸和琥珀酰辅酶A缩合生成5-氨基乙酰丙酸。对于反应中的初始C-C键形成步骤，可以考虑至少两个宽的途径。在途径A中，甘氨酸的席夫碱和酶结合的磷酸吡哆醛（a）经历脱羧以产生负碳离子（B），其然后与琥珀酰辅酶A缩合，同时保留甘氨酸的两个原始C2氢原子。在途径B中，C2氢原子的损失产生另一种类型的碳负离子（c），其与琥珀酰辅酶A反应。已经提出的证据表明，初始C-C键形成事件通过途径B发生，该途径涉及去除甘氨酸的proR氢原子。随后的机制和立体化学事件发生在碳原子注定成为C5的5-氨基乙酰丙酸酯也已划定。
5-Aminolaevulinate synthetase catalyses the condensation of glycine and succinyl-CoA to give 5-aminolaevulinic acid. At least two broad pathways may be considered for the initial C—C bond forming step in the reaction. In pathway A the Schiff base of glycine and enzyme bound pyridoxal phosphate (a) undergoes decarboxylation to give the carbanion (b) which then condenses with succinyl-CoA with the retention of both the original C2 hydrogen atoms of glycine. In pathway B, loss of a C2 hydrogen atom gives another type of carbanion (c) that reacts with succinyl-CoA. Evidence has been presented to show that the initial C—C bond forming event occurs via pathway B which involves the removal of the proRhydrogen atom of glycine. Subsequent mechanistic and stereochemical events occurring at the carbon atom destined to become C5 of 5-aminolaevulinate have also been delineated.