PRPP amido-transferase

Misawa et al, 1969). Such cultures require guanine for growth and levels added to the medium must be kept low to bypass feedback effects on enzyme (IMP dehydrogenase) and enzyme a (PRPP amido-transferase). 

C-4) Overactivity of either PRPP synthetase (which acts between ribose 5-P and PRPP) or amido-transferase (which acts between PRPP and 5-P-ribosylamine). A modification of these enzymes may lead to their overactivity, with consequent hyperuricemia. 

In the first committed step of the purine biosynthetic pathway, PRPP reacts with glutamine to form phosphoribosylamine (Fig. 41.4). This reaction, which produces nitrogen 9 of the purine ring, is catalyzed by glutamine phosphoribosyl amido-transferase, a highly regulated enzyme. 

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