Deoxyribosyl Transfer Catalysis with <i>trans‐N</i>‐Deoxyribosylase

Abstract

Kinetic studies were carried out in order to investigate the enzymic mechanism of a 1420‐fold purified purine nucleoside : purine deoxyribosyl transferase fraction from Lactobacillus helveticus. Deoxyinosine and adenine were used as substrates. Initial velocity, product inhibition and isotopic exchange studies are consistent with a ping‐pong bi‐bi mechanism (the first product is released before the second substrate combines with the enzyme). The numerical values of the Michaelis and dissociation constants, maximum velocities and equilibrium constants for the forward and reverse reactions are derived graphically from secondary plots. A comparison with purine nucleoside phosphorylase is discussed.