核苷酸
生物合成
肌苷
肌苷酸
生物化学
次黄嘌呤
鸟苷
核苷酸
化学
从头合成
鸟苷酸
嘌呤代谢
嘌呤
腺苷
立体化学
酶
基因
标识
DOI:10.1002/9781119476139.ch4
摘要
The de novo biosynthesis of purine nucleotides was elucidated independently by J. M. Buchanan and Greenberg in the 1950s. Substantial amounts of ureides are produced as the major nitrogen-containing compounds derived from purine nucleotides. This chapter describes the reaction and enzymes of de novo purine nucleotide biosynthesis. There are 10 steps from 5-phosphoribosyl-1-pyrophosphate (PRPP) to inosine-5′-monophosphate (IMP). Adenosine-5′-monophosphate (AMP) and guanosine-5′-monophosphate (GMP) are then produced by two steps from IMP. Purine biosynthesis de novo starts with the formation of phosphoribosylamine from PRPP and glutamine. The last two steps to form IMP, the first complete purine nucleotide, are catalysed by the bifunctional enzyme 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase. AMP and GMP are synthesized from IMP. AMP is formed by replacing the carboxyl group at C6 with an amino group from aspartate. Synthesis of GMP is initiated by the oxidation of IMP followed by the insertion of an amino group that is provided by glutamine.
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