NUCLEOSIDE INTERMEDIATES IN BLASTICIDIN-S BIOSYNTHESIS IDENTIFIED BY THE IN-VIVO USE OF ENZYME-INHIBITORS

Intermediates in the biosynthesis of blasticidin S and its nucleoside co-metabolites were detected by altering fermentation conditions. Inhi bitors of specific types of biochemical reactions that were expected t o be involved in blasticidin biosynthesis were fed to Streptomyces gri seochromogenes, in some cases with the inclusion of large quantities o f the primary precursors of blasticidin S. The types of reactions and inhibitors used were (1) transaminase (aminooxyacetic acid and 2-methy lglutamate), (2) amidotransferase (azaserine and 6-diazo-5-oxo-L-norle ucine), (3) arginine biosynthesis (arginine hydroxamate), and (4) meth yltransferase (ethionine). These manipulations apparently distorted th e pools of precursors and (or) intermediates, and led to substantial a ccumulations of three known, previously minor, metabolites of S. grise ochromogenes, cytosylglucuronic acid, pentopyranine C, and demethylbla sticidin S, and of two new ones, pentopyranone and isoblasticidin S. N ew cytosyl metabolites were detected by HPLC with photodiode array det ection. Fermentations to which arginine hydroxamate and cytosine had b een added also produced three aberrant metabolites that were derived f rom pentopyranone and arginine hydroxamate.