The Effects of the Medium’s pH Value on the Efficiency of the Enzymatic Transglycosylation Catalyzed by Escherichia coli Purine Nucleoside Phosphorylase and Lactobacillus leichmanii Nucleoside Deoxyribosyltransferase Type II

The effect of the reaction medium pH value on the rate and yield of enzymatic transglycosylation catalyzed by Escherichia coli purine nucleoside phosphorylase (EcPNP) and Lactobacillus leichmanii type II nucleoside deoxyribosyltransferase (LlNDTII) was investigated. In the presence of EcPNP at pH 5.5, a significant reduction in the inosine formation rate was observed, compared with that of adenosine. A substituent at the purine O6 position neutralizes the negative effect of the 6-oxo group on the reaction rate. A substituent at the purine N6 position has virtually no effect on the transglycosylation rate. In reactions catalyzed by LlNDTII, the rate of nucleoside formation from 4-oxopyrimidines was higher at pH 5.5, but the yield decreased by approximately 10% compared with that at pH 7.0; an unusual dependence of the yield of the target nucleoside on the enzyme concentration used was also revealed.