Nucleotide interconversions. X. Deoxyribo- and ribonucleoside 5′-phosphate synthesis via a phosphotransferase reaction in chick embryo extracts

Abstract

Chick embryo extracts have been found to promote the transfer of phosphate from nucleoside 5′-phosphates to the 5′-hydroxymethyl group of nucleosides. Although the pyrimidine ribonucleosides were the preferred acceptors of phosphate from the pyrimidine ribonucleotides, the most efficient reactions appeared to involve transfer between the pyrimidine deoxyribonucleotides and pyrimidine deoxyribonucleosides. The in vitro synthesis of deoxyribonucleotides by the phosphotransferase reactions was more active than the syntheses promoted by ATP kinases; however, dialysis of the extracts, while resulting in a sharp reduction of phosphotransferase activity, did not appear to affect the kinase reactions, except for the distribution of products formed. The primary product resulting from the reaction of dTMP with d -cytidine in chick embryo extracts was dCMP, whereas the reaction of ATP with d -cytidine yielded dUMP and d -uridine as the major products. With adult chicken liver extracts, the major phosphotransferase product resulting from the reaction of dTMP and d -cytidine was dUMP. A two-step reaction appeared to be involved in the formation of the latter compound: d − cytidine → d − uridine → dTMP dUMP