The biosynthesis of the 7-deazaadenine ribonucleoside, tubercidin, by Streptomyces tubercidicus.

Studies on the biosynthesis of the 7-deazaadenine base of the antibiotic, tubercidin, in growing cultures of Streptomyces tubercidicus are described. Isotope incorporation patterns suggest that the pyrimido moiety of a purine serves as the precursor of the pyrimido portion of 7-deazaadenine and that carbon atoms 1 and 2 of ribose may be incorporated into the pyrrole moiety of 7deazaadenine. These conclusions are based on the following ezperimental observations. Carbon atom 8 of adenine8J4C is metabolized to r4C02 during the biosynthesis of tubercidin. 14C from adenine-2J4C, but not adenine-8J4C, is incorporated into 7-deazaadenine. The extents of incorporation of glycine and formate into cellular adenine and 7-deazaadenine are similar. The addition of adenine to cultures of S. tubercidicus inhibits the incorporation of 14C from glycine-lJ4C into both cellular adenine and 7-deazaadenine. Ribose-1-W is incorporated into the 7-deazaadenine ring. The amide nitrogen of the glutamine and the amino nitrogen of aspartic acid are incorporated into 7deazaadenine. The implications of these findings with respect to the biological transformation of purines to 7deazaadenine are discussed.