Adenylsuccinate synthetase

A vej atile procedure for the introduction of alkyl, epoxyalkyl groups into heterocycles, which Involves displacement of leaving groups by Wittig reagents, followed by appropriate manipulation of the resulting ylides, has been applied to the synthesis of various 6-substl ted purines designed as inhibitors of adenylsuccinate synthetase and lyase. 

P.b. is regulated by both end products, AMP and GMP, which jointly inhibit phosphoribosylpyrophos-phate amidotransferase (EC 2.4.2.14). GMP also inhibits IMP-dehydrogenase (EC 1.2.1.14) AMP inhibits adenylsuccinate synthetase (EC 6.3.4.4). Further control is exerted by the requirement for GTP in AMP synthesis (Fig.2). ATP inhibits GMP reductase, which converts GMP into IMP in one step. 

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