Essential arginine residues in tryptophanase from Escherichia coli.

摘要: Tryptophanase from Escherichia coli B/1t7-A is inactivated by the arginine-specific reagent, phenylglyoxal, in potassium phosphate buffer at pH 7.8 AND 25 degrees. Apo- and holoenzyme are same rate, inactivation of both correlated with modification 2 arginine residues/tryptophanase monomer. Substrate analogs having a carboxyl group protect against but have no effect on or apoenzyme. Phenylglyoxal-modified apotryptophanase retains capacity to bind coenzyme, pyridoxal-P, spectrum this reconstituted species differs that native holotryptophanase. Neither nor phenyglyoxal-modified shows 500 nm absorption characteristic enzyme when substrates added. These results demonstrate requirement for specific residues substrate binding discussed context known conformational spectal forms tryptophanase regard possible role formation catalytically effective enzyme-pyridoxal-P complex.