Essential arginine residue in gramicidin S synthetase 1 of Bacillus brevis.

Phenylalanine activation of gramicidin S synthetase 1 (GS 1) [EC 5.1.1.11] of Bacillus brevis is inhibited by phenylglyoxal. The inactivation of GS 1 by phenylglyoxal obeys pseudo-first-order kinetics and formation of a reversible enzyme-reagent complex prior to modification is indicated. Both ATP and phenylalanine prevent the inactivation by phenylglyoxal. ATP is competitive with phenylglyoxal, whereas phenylalanine is not. In the presence of ATP, one residue of arginine per mol of protein is protected from the modification as determined by amino acid analysis and incorporation of [7-14C]phenylglyoxal. These results indicate that a single arginine residue of GS 1 is essential for phenylalanine activation in binding the phosphate moiety of ATP.