SYNTHESIS OF PURINE INTERMEDIATES BY A CELL-FREE EXTRACT OF ESCHERICHIA COLI

Abstract

Cell-free extracts of Escherichia coli strain W-11 were prepared which can synthesize purine intermediates from elementary precursors. Glutamine, ribose-5-phosphate, adenosine tri-phosphate and phosphoglyceric acid are necessary substrates for this biosynthetic reaction. The main product of the reaction is 5-amino-4-imidazolecarboxamide ribotide. This finding contrasts with the results obtained with whole cells in which mainly 5-aminoimidazole riboside is produced. It was believed previously that strain W-ll possesses a genetic block which prevents conversion of 5-aminoimidazole compounds to 5-amino-4-imidazolecarboxamide ribotide and to purines. The experiments with extracts show, however, that this metabolic block is not caused by a lack of enzymes required for further metabolism of 5- aminoimidazole compounds.