Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: Isolation and characterization of a mutant deficient in the activity of phosphoribosylaminoimidazole synthetase

Abstract

A new purine-requiring mutant of Chinese hamster ovary cells (CHO-Kl) is described. This mutant, Ade⁻ G, grows on aminoimidazole carboxamide, hypoxanthine, or adenine. It complements all eight of our other previously described Ade⁻ mutants. Biochemical analysis of de novo purine synthesis in whole cells suggests that Ade⁻ G is capable of the first four reactions of de novo purine biosynthesis and that it synthesizes and accumulates phosphoribosylformylglycinamidine (FGAM). Direct enzyme assay in cell-free extracts confirms that Ade⁻ G is defective in phosphoribo-sylaminoimidazole synthetase activity and does not convert FGAM to phosphoribosylaminoimidazole (AIR), the next intermediate in the de novo biosynthetic pathway.