Streptomycin Biosynthesis and Metabolism

Abstract

Abstract A number of novel monophosphorylated aminocyclitol derivatives have been prepared enzymatically, utilizing the phosphotransferase activity of enzyme preparations containing streptomycin 6-phosphate phosphatase, an enzyme believed to catalyze the final step in the biosynthesis of streptomycin by Streptomyces. Aminodeoxyinositols, streptamine (1,3-diamino-1,3-dideoxy-scyllo-inositol), and 2-deoxystreptamine, at concentrations in the millimolar range, compete effectively with 55 m water for phosphate transferred by these enzyme preparations from either dihydrostreptomycin 6-[32P]phosphate or p-nitrophenyl phosphate. Phosphate is preferentially esterified by action of streptomycin 6-phosphate phosphatase preparations with hydroxyl groups ortho to amino groups of aminocyclitol acceptors; in contrast, ATP:aminocyclitol kinase phosphorylates hydroxyl groups para to specific amino groups of its aminocyclitol substrates. One of the several phosphorylated streptamine isomers formed by action of streptomycin 6-phosphate phosphatase preparations on streptamine appears to be identical with the product formed by action of ATP:aminocyclitol kinase on streptamine, 1l-1,3-diamino-1,3-dideoxy-scyllo-inositol 4-phosphate, as judged by ability of both reaction products to act as substrates for l-arginine:aminocyclitol 4-phosphate amidinotransferase. Analogous results were obtained with 2-deoxystreptamine. This occurs because in streptamine and 2-deoxystreptamine a phosphate group ortho to one amino group can be para to the other amino group. None of the phosphorylated aminodeoxy-scyllo-inositol isomers formed by action of streptomycin 6-phosphate phosphatase preparations was a substrate for aminocyclitol 4-phosphate amidinotransferase. These results support our structural assignments for phosphorylated intermediates in the biosynthesis of the streptidine moiety of streptomycin.