Streptomycin biosynthesis. I. Existence of two amidinotransferase activities in Streptomyces griseus

Abstract

1. 1. A cell-free extract with amidinotransferase activity ( l-arginine:X amidinotransferase, EC class 2.1.4.) was obtained from frozen mycelia of Streptomyces griseus by shaking at 25° with 3 vol. of 0.1 M phosphate buffer (pH 7.4) containing 3 mg/ml EDTA. 2. 2. By thermal inactivation of the cell-free extract at 45° two amidinotransferase activities were detected, distinguishable by their temperature sensitivities. 3. 3. The enzymes were purified 4-fold by DEAE-Sephadex adsorption, (NH 4) 2SO 4 fractionation and column chromatography on the same Sephadex. 4. 4. In the column chromatography two protein peaks were obtained, both with amidinotransferase activities, which correspond to the ones detected by thermal inactivation. 5. 5. The question is discussed whether these two amidinotransferase activities correspond to two isoenzymes or to active subunits of a single enzyme, or whether they are two different enzymes with their specific physiological substrates, O-phosphoryl- scyllo-inosamine and O-phosphoryl- N-amidinostreptamine, both precursors of the streptomycin molecule.