title: Demonstration of a metabolic grid at an early step in the streptonigrin biosynthetic pathway in Streptomyces flocculus.
abstract: The enzyme activities which catalyze the conversion of tryptophan to beta-methyltryptophan by two different routes have been demonstrated in cell-free extracts of streptonigrin-producing Streptomyces flocculus. The first route involves direct methylation of tryptophan by a C-methyltransferase. The second involves transamination of tryptophan to indolepyruvate, methylation of indolepyruvate to beta-methylindolepyruvate, followed by a reverse transamination reaction to yield beta-methyltryptophan. The direct methylation route was confirmed by the fact that the methyltransferase activity is still present after the transaminase has been inactivated by hydroxylamine treatment. The L-tryptophan C-methyltransferase has been purified 30-fold by ammonium sulfate precipitation and a Sephadex G-150 column. The indolepyruvate C-methyltransferase activity copurified with the tryptophan C-methyltransferase activity, but the transaminase did not. These results show that a metabolic grid exists for the first antibiotic-committed step of the streptonigrin biosynthetic pathway.
mesh_terms: D008745:Methylation; D008780:Methyltransferases / Q000032:analysis; D013302:Streptomyces / Q000378:metabolism*; D013308:Streptonigrin / Q000096:biosynthesis*; D000637:Transaminases / Q000032:analysis; D014364:Tryptophan / Q000378:metabolism
chemical_list: D013308:Streptonigrin; D014364:Tryptophan; D008780:Methyltransferases; D000637:Transaminases