The Beneficial Effect of Organic Solvents on the Enzymatic Synthesis of Nucleoside Analogues Using N-Deoxyribosyltransferases fromLactobacillus leichmannii(E.C. 2.4.2.6)

Addition of ethylene glycol (10% v/v) has a beneficial effect on the synthesis of 2′-deoxynucleosides catalysed by crude preparations of N-deoxyribosyltransferases from Lactobacillus leichmannii. In the absence of added organic solvent decomposition of products and starting materials by deamination or hydrolysis occurs giving rise to poor yields of products if the transfer reaction is slow. The glycosyl transfer reaction is unaffected by addition of organic solvent but decomposition of products and starting materials is largely suppressed. The organic solvent appears to inhibit selectively contaminating enzymes in the crude N-deoxyribosyltransferase preparation as the purified transferase does not possess hydrolytic or deaminating activity. Different concentrations of ethylene glycol and other organic solvents have been examined as inhibitors of the side reactions but 10% (v/v) appears to be the most effective. Using the N-deoxyribosyltransferase in the presence of ethylene glycol, a number of 2′-deoxynucleosides of 6-substituted nucleosides have been obtained in high yield on a preparative scale.