Abstract
The production, isolation, and characterization of a new complementation group (AdeI)of adenine-requiring mutant of Chinese hamster cells (CHO-K1) is described. This mutant accumulates two intermediates of purine biosynthesis, both of which contain an aspartate moiety. One of these is shown to be adenylosuccinic acid (AMPS) by Chromatographic analysis, while evidence is presented that strongly suggests the other intermediate is succinylaminoimidazole carboxamide ribotide (SAICAR). Thus, AdeIis most likely lacking the activity of the enzyme adenylosuccinase (EC 4.3.2.2). The use of this and similar mutants for the analysis of regulation of purine biosynthesis in mammalian cells is discussed.