title: A purine auxotroph deficient in phosphoribosylpyrophosphate amidotransferase and phosphoribosylpyrophosphate aminotransferase activities with normal activity of ribose-5-phosphate aminotransferase.
abstract: Three enzyme reactions have been reported to catalyze the synthesis of phosphoribosylamine in eukaryotic cells. These activities are glutamine phosphoribosylpyrophosphate (P-Rib-P-P) amidotransferase [amidophosphoribosyl-transferase; 5-phosphoribosylamine: pyrophosphate phosphoribosyltransferase (glutamate-amidating) EC 2.4.2.14], ammonia P-Rib-P-P aminotransferase, and ammonia ribose-5-phosphate aminotransferase. A purine auxotroph derived from a cell line  of Chinese hamster fibroblasts was shown to be deficient in catalytic activities of glutamine P-Rib-P-P amidotransferase and ammonia P-Rib-P-P aminotransferase. Extracts from this cell line had normal ammonia ribose-5-phosphate aminotransferase activity. The defect in purine biosynthesis in the mutant cell line was localized to the synthesis of phosphoribosylamine. These results indicate that glutamine P-Rib-P-P amidotransferase or ammonia P-Rib-P-P aminotransferase or both are important for phosphoribosylamine synthesis, but that ammonia ribose-5-phosphate aminotransferase activity probably does not play a significant role in this eukaryotic cell line. The simultaneous disappearance of both P-Rib-P-P-dependent activities suggests these two enzyme activities are closely related structurally or genetically.
mesh_terms: D000582:Amidophosphoribosyltransferase / Q000172:deficiency*; D000641:Ammonia; D002460:Cell Line; D008025:Ligases / Q000378:metabolism*; D010428:Pentosephosphates / Q000096:biosynthesis*; D010430:Pentosyltransferases / Q000172:deficiency*; D010754:Phosphoribosyl Pyrophosphate; D011687:Purines / Q000096:biosynthesis; D012267:Ribosemonophosphates / Q000096:biosynthesis*; D000637:Transaminases / Q000172:deficiency*
chemical_list: D010428:Pentosephosphates; D011687:Purines; D012267:Ribosemonophosphates; D010754:Phosphoribosyl Pyrophosphate; D000641:Ammonia; D010430:Pentosyltransferases; D000582:Amidophosphoribosyltransferase; D000637:Transaminases; D008025:Ligases