STREPTOMYCIN BIOSYNTHESIS . TRANSAMINATION REACTONS INVOLVING INOSAMINES AND INOSADIAMINES

In the biosynthesis of the streptidine moiety of streptomycin from myoinositol, the two nitrogen atoms on the cyclitol ring are introduced by transamination of inosose derivatives. The two transaminase activities have been separated on a Sephadex G-100 column; pyridoxal phosphate must bepresent during the separation to retain activity. The first transaminase to emerge from the column was L-glutamine-scyllo-inosose transaminase, which catalyzes the first reaction unique to streptidine biosynthesis. scyllo-Inosamine, a known precursor of streptidine in cell-free preparations, is aproductof this reaction. Enzyme preparations containing this activity also catalyze the following transaminations : scyllo-inosamine-scyllo-inosose, 2-deoxystreptamine- scyllo-inosose, scyllo-inosamine-myo-inosose- 4(6), myo-inosamine-6-scyllo-inosose, streptamine-scyllo-inosose, L-alanine-scyllo-inosose, and scyllo-inosamine- pyruvate. The second amino group is added to the cyclitol ring in areaction catalyzed by L-alanine- L-amidino-3- (or 5-) keto-scyllo-inosamine transaminase. N-Amidinostreptamine is a product of this reaction. L-Glutamate is the next most effective amino donor, followed by L-glutamine. Enzyme preparations containing this activity also catalyze the following transaminations: N-amidinostreptamine-pyruvate, N-amidinostreptamine- α-ketoglutarate, and N-amidinostreptamine- N-amidino-3- (or 5-) keto-scyllo-inosamine. At concentrations higher than those required for glutamine-scyllo-inosose transaminase, scyllo-inosose can serve as an amino acceptor fromN-amidinostreptamine, and scyllo-inosamine as an amino donor to ZV-amidino-3- (or 5-) keto-scyllo-inosamine. © 1969, American Chemical Society. All rights reserved.