Catalytic properties of the PepQ prolidase from Escherichia coli

Abstract The PepQ prolidase from Escherichia coli catalyzes the hydrolysis of dipeptide substrates with a proline residue at the C-terminus. The pep Q gene has been cloned, overexpressed, and the enzyme purified to homogeneity. The k cat and k cat / K m values for the hydrolysis of Met-Pro are 109 s −1 and 8.4 × 10 5  M −1  s −1 , respectively. The enzyme also catalyzes the stereoselective hydrolysis of organophosphate triesters and organophosphonate diesters. A series of 16 organophosphate triesters with a p -nitrophenyl leaving group were assessed as substrates for PepQ. The S P -enantiomer of methyl phenyl p -nitrophenyl phosphate was hydrolyzed with a k cat of 36 min −1 and a k cat / K m of 710 M −1  s −1 . The corresponding R P -enantiomer was hydrolyzed more slowly with a k cat of 0.4 min −1 and a k cat / K m of 11 M −1  s −1 . The PepQ prolidase can be utilized for the kinetic resolution of racemic phosphate esters. The PepQ prolidase was shown to hydrolyze the p -nitrophenyl analogs of the nerve agents GB (sarin), GD (soman), GF, and VX.