Biosynthesis of tyrocidine by A cell-free enzyme system of Bacillus brevis ATCC 8185 II. Amino acid substitution in tyrocidine

Abstract

1. 1. The partially purified tyrocidine-synthesizing system of Bacillus brevis ATCC 8185 was revealed to have the ability to synthesize tyrocidines A, B, C and D. 2. 2. The enzyme system is not absolutely specific for particular amino acids. A new tyrocidine, tyrocidine E (tyrosine residue in tyrocidine A was replaced by phenylalanine), lysyl-tyrocidine A (ornithine residue in tyrocidine A was replaced by lysine) and isoleucyl-tyrocidine A (leucine residue in tyrocidine A was replaced by isoleucine) were synthesized in vitro. 3. 3. A single enzyme system catalyzed the synthesis of these tyrocidines and their formation was directly influenced by the amino acid concentrations in the reaction mixture. 4. 4. Some amino acid analogues, such as 5-methyltryptophan, p-fluorotryptophan, thienylalanine and p-fluorophenylalanine promoted the ATP- 32PP 1 exchange reaction and were incorporated into tyrocidine.