BIOCHEMICAL GENETICS OF CHINESE-HAMSTER CELL MUTANTS WITH DEVIANT PURINE METABOLISM - ISOLATION AND CHARACTERIZATION OF A MUTANT DEFICIENT IN THE ACTIVITY OF PHOSPHORIBOSYLAMINOIMIDAZOLE SYNTHETASE

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. © 1979 Plenum Publishing Corporation.