title: Studies on gramicidin S synthetase. Purification and properties of the light enzyme obtained from some mutants of Bacillus brevis.
abstract: The phenylalanine-activating and/or-racemizing enzyme, i.e., the light enzyme, of gramicidin S synthetase was purified to a homogenous state by D-phenylalanine-Sepharose 4B chromatography from a wild and some gramicidin S-lacking mutant strains of Bacillus brevis. The light enzyme obtained from a mutant strain E-1 could activate phenylalanine but not racemize it, and had no phenylalanine-dependent ATP-[14C]AMP exchange activity, whereas the same enzyme obtained from other mutants and the wild strain had all three activities. Furthermore, the light enzyme of the mutant E-1 could form only acid-labile enzyme-bound phenylalanine, while the same fraction of the wild strain carried half of the enzyme-bound phenylalanine as acid-labile adenylate and half as a acid-stable thioester. These results suggest that the thiol site of the light enzyme of mutant E-1 might be damaged.
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D049148:Aminoacylation; D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D006096:Gramicidin / Q000096:biosynthesis; D008970:Molecular Weight; D009097:Multienzyme Complexes; D009154:Mutation; D010453:Peptide Synthases; D010649:Phenylalanine; D013045:Species Specificity
chemical_list: D009097:Multienzyme Complexes; D006096:Gramicidin; D010649:Phenylalanine; D000591:Amino Acid Isomerases; D010453:Peptide Synthases