Streptomyces R61 dd-carboxypeptidase: Hydrolysis of X-d-alanyl-d-alanine peptides measured by a fluorometric assay

Abstract A fluorometric procedure for measuring the activity of dd -carboxypeptidase is described. The method is based on the reaction of one of the products, d -alanine, with o -phthaldialdehyde to form a highly fluorescent adduct. The method has been applied in examining a series of X - d -alanyl- d -alanine peptides as substrates of the penicillin-sensitive dd -carboxypeptidase from Streptomyces R61. The effect of the third residue, X , on kinetic parameters and its implications on the steric analog model for penicillin action are also discussed.