The enzymically catalysed transfer of the deoxyribosyl group from one purine or pyrimidine to another

Abstract

Dialyzed enzyme prepns. from Lactobacillus helveticus were shown by indirect methods to catalyze the transfer of the desoxyribosyl group from one purine or pyrimidine to another. By these methods uracil desoxyriboside, thymine desoxyriboside, 5-methylcytosine desoxyriboside, and cytosine desoxyriboside were shown to be formed by the interaction of the corresponding pyrimidine and purine desoxyribosides. Orotic acid was not tested. Orotic acid was not tested. Conversely; substances which showed the lability to mild acid hydrolysis characteristic of purine desoxyribosides were formed when pyrimidine desoxyribosides reacted enzymically with adenine, guanine, hypoxanthine, xanthine, and 4-amino-glyoxaline-5-carbonamide. Uric acid, 2,6-diaminopurine, and certain other compounds were inactive. The transfer was catalyzed in phosphate-free buffers by enzyme prepns. which had been dialyzed for several days. Neither desoxyribose nor desoxyribose-1-phosphate was active in the transfer reaction. The enzyme involved is considered to be a trans-N-glycosidase, analogous to the trans-O-glycosidase from Pseudomonas saccharophila (Dou-doroff et al. 1947). Enzyme prepns. from 2 other desoxyri-boside-requiring bacteria (L. delbrueckii and Thermobacterium acidophilus R 26) also catalyzed the transfer. An attempt to demonstrate the trans-reaction in living cells of Leuconostoc citrovorum was unsuccessful.