Deoxyribosyl Transfer Catalysis with trans ‐ N ‐Deoxyribosylase

Abstract

Kinetic studies were carried out in order to investigate the enzymic mechanism of a 215‐fold‐purified purine(pyrimidine) nucleoside: purine(pyrimidine) deoxyribosyl transferase fraction from Lactobacillus helveticus . A variety of natural deoxyribonucleosides and bases were used as substrates. Initial velocity, product inhibition and isotopic exchange studies are consistent with a ping‐pong bi‐bi mechanism. The kinetic parameters are used to show that this fraction is free from any contamination by a specific purine nucleoside: purine deoxyribosyl transferase also found in the same strain of L. helveticus .