Penicillin G acylase (PGA) is an important enzyme for the industrial production of 7-amino-3-deacetoxy cephalosporanic acid (7-ADCA) from cephalosporin G (Ceph-G), and 6-aminopenicillanic acid (6-APA) from penicillin G (Pen-G). These products are used for the manufacture of semi-synthetic cephalosporins and penicillins. In this study, immobilized PGA was utilized to catalyze the conversion of Ceph-G to 7-ADCA. The optimal conditions were found to be an operating temperature of 45degreesC, 0.2 M phosphate buffer, a substrate concentration of 30 mg cm(-3) and a catalyst particle concentration of 0.01 g cm(-3) (specific activity of 623.2 U g(-1)). Up to 45degreesC the reaction was characterized by an activation energy of 38.66 kj mol(-1) . Beyond 57.5degreesC there was a sharp decline of. activity, characterized by a deactivation energy of 235.88 kj mol(-1). (C) 2004 Society of Chemical Industry.