ENZYMATIC SYNTHESIS OF ACTINOCINYL PEPTIDES

The enzyme, phenoxazinone synthetase, purified 25- to 30-fold from cell-free extracts of Streptomyces antibioticus catalyzes the formation of the actinomycin chromophore, actinocin, when 4-methyl-3-hydroxyanthranilic acid (4-MHA) is employed as substrate. When 4-methyl-3-hydroxyanthraniloyl peptides (4-MHA-l-threonyl-d-valine, 4-MHA-l-threonyl-d-valyl-l-proline, 4-MHA-l-threonyl-d-valyl-l-prolylsarcosine and 4-MHA-l-threonyl-d-valyl-l-prolyl-sarcosyl-N-methyl-l-valine) were used, actinocinyl peptides were readily synthesized by the enzyme. A number of o-aminophenols will serve as substrates; however, compounds such as 3-amino-4-hydroxybiphenol, 2-amino-4-tert-butylphenol and 3-amino-2-naphthol proved to be excellent inhibitors of the enzymatic reaction. Generally, benzene ring compounds possessing an amino group but lacking an hydroxyl group were good to excellent inhibitors, whereas compounds containing an hydroxyl group but lacking an amino substituent (or possessing a substituted one) were poor to moderate inhibitors. Anthranilic acid (o-aminobenzoic acid) was found to be a competitive inhibitor of the reaction suggesting a relationship between the metabolism of tryptophan and antibiotic production. © 1969.