Properties of 5′-phosphoribosylpyrophosphate amidotransferase in virus induced murine leukemia

Abstract

Virus-induced 5′-phosphoribosylpyrophosphate amidotransferase (ribosylamine 5′-phosphate:pyrophosphate phosphoribosyltransferase (glutamate amidating). (EC 2.4.2.14), the first enzyme in purine biosynthesis, was isolated from spleens of mice infected with Friend leukemia virus, purified and certain of its properties were studied. The enzyme, which catalyzes the synthesis of 5′-phosphoribosylamine has a requirement for two substrates: 5′-phosphoribosyl pyropyhosphate as the phosphoribosyl donor, and for a nitrogen containing compound as a source of the amino group of 5′-phosphoribosylamine. Ribose 5-phosphate could not replace 5′ phosphoribosyl pyrophosphate. Nitrogen containing compounds found to be substrates were NH 4Cl, (NH 4) 2SO 4 and glutamine. The enzyme was sensitive to inhibition by purine ribonucleotides. Inhibition was competitive with 5′-ribosyl pyrophosphate and glutamine, but non competitive with respect to NH 4Cl.