Activite de donateurs d'azote des derives formimines au cours de la biosynthese des purines chez Escherichia coli B

Abstract

Nitrogen donor activity of the formimino compounds during purine biosynthesis in Escherichia coli B The nitrogen donor activity of the natural formimino-compounds, formimino-glutamic and -aspartic acids and formimino-glycine during purine biosynthesis has been studied in Escherichia coli B. 1. 1. The imino-nitrogen of the formimino-compounds is actively incorporated into 5-amino-4-imidazolecarboxamide (AICA) by partially sulfadiazine-inhibited growing cells of E. coli B. This incorporation is enhanced while that of free ammonia ions is decreased by glutamine. These results indicate that the incorporation of the imino-nitrogen into AICA does not proceed with glutamine as an intermediate and that the mechanism of utilization of the imino-nitrogen is different from that of ammonia ions. 2. 2. The incorporation of [ 14C]glycine into the precursor of AICA, 5′-phosphoribosyl-formylglycinamide, and into nucleic acid purines of azaserine-inhibited non-proliferating cells of E. coli shows that the formimino-derivatives exert their nitrogen donor activity specifically during the reaction catalyzed by the 5′-phosphoribosyl-formylglycinamide: l-glutamine amido-ligase (ADP) (EC 6.3.5.3). Results obtained with cells of which the activity of glutamine synthetase is strongly repressed and additionally inhibited by methionine sulfoximine further confirm that the imino-nitrogen is used directly in the synthesis of phosphoribosyl-formylglycinamidine and not with glutamine as an intermediate. The nitrogen donor activities of formimino-glutamic acid and glutamine are approximately identical.