New possibilities of enzyme synthesis of radioactive nucleotides. II. Phosphoribosylation of radioactive bases of nucleic acids by the catalytic effect of unpurified cell‐free extract of Brevibacterium ammoniagenes

Abstract

The catalytic properties of an unpurijied enzyme preparation from cells of Brevibacterium ammoniagenes toward phosphoribosylation of the individual nucleic acid bases are pronouncedly specijic, display a high efficiency toward phosphoribosylation of uracil where the conversion to uridine-5'-phosphate is quantitative, phosphoribosylation of adenine takes place with lower eflciency and guanine and cytosine are practically not phosphoribosylated at all. Using orotic acid-14C and a complete inhibition of orotidine 5'-phosphate decarboxylase by means of 6-azauridine-5'-phosphate, a 60 % production of orotidine-5'-phosphate-14C has been achieved.The catalytic efficiency of the enzyme preparation remains preserved even upon substitution of 5-phosphoribosyl-I-pyrophosphate by its direct metabolic precursors.The possibility of direct application of the unpurijied cell-free extract of the bacteria, the simple composition of the jinal reaction mixtures and the high degree of production of biologically important compounds makes it possible to employ the method studied for an enzyme synthesis of radioactive uridine-5'-phosphate, orotidine-5'-phosphate and adenosine-5'-phosphate.