Enzymatic Synthesis of 5′-Phosphoribosylamine from Ribose 5-Phosphate and Ammonia, an Alternate First Step in Purine Biosynthesis
1968; Elsevier BV; Volume: 243; Issue: 21 Linguagem: Inglês
10.1016/s0021-9258(18)91922-8
ISSN1083-351X
Autores Tópico(s)HIV/AIDS drug development and treatment
ResumoAbstract An enzyme activity responsible for the formation of 5'-phosphoribosylamine from ribose 5-phosphate and a nitrogen donor was prepared from livers of ducks, chickens, and pigeons. This enzyme activity is distinct from ribosylpryophosphate 5-phosphate amidotransferase (EC 2.4.2.14), which catalyzes the formation of 5'-phosphoribosylamine from ribosylpyrophosphate 5-phosphate and glutamine. The enzyme was partially purified and completely separated from ribosylpyrophosphate 5-phosphate amidotransferase. For maximal synthesis of 5'-phosphoribosylamine, the reaction required ribose 5-phosphate, ammonium chloride, ATP, and magnesium ions. Prolonged heating at 80° destroyed the activity of the enzyme. It is proposed that an alternate pathway for the initial step of purine synthesis exists, namely, the direct conversion of ribose 5-phosphate to 5'-phosphoribosylamine. This reaction is enzymatic and is sensitive to inhibition by ribonucleotides and by ribose 5-phosphate.
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