Penicillin acylase-catalyzed synthesis of pivampicillin: Effect of reaction variables and organic cosolvents

Abstract

Enzymatic synthesis of pivampicillin (PVM) from D-alpha-phenylglycine methyl ester (PGM) and pivaloyloxymethyl 6-aminopenicillanic acid (POM-6-APA) was investigated using an immobilized Escherichia coli penicillin acylase. The effects of reaction variables such as enzyme concentration, pH, temperature, and molar ratio of the substrates on PVM synthesis were investigated, The time-course profiles of the PVM synthesis reaction followed a typical pattern of the kinetically-controlled synthesis of beta-lactam antibiotics: the concentration of PVM reached a maximum and then decreased gradually. By lowering the reaction temperature, the maximum yield was enhanced significantly. This was mainly attributed to the suppressed hydrolysis of PVM and PGM at low temperatures. A higher yield of PVM was also attained with increasing the molar ratio of PGM to POM-6-APA. When the molar ratio of PGM to POM-6-APA was 10, the maximum yield of 61.8% was obtained at 4 degrees C. The addition of organic cosolvents, on the other hand, showed no improvement in the PVM synthesis yields due to inhibitory effect of the solvent; both synthetic and hydrolytic activities of penicillin acylase were reduced by organic solvents. The degree of inhibition was found to be more profound in the presence of less polar solvents.