Kinetic study on substrate and product inhibitions for the formation of 7-amino-3-deacetoxy cephalosporanic acid from cephalosporin G by immobilized penicillin G acylase

Penicillin G acylase (PGA) is an important enzyme in β-lactam antibiotics pharmaceutical industry for the production of 7-amino-3-deacetoxy cephalosporanic acid (7-ADCA) from cephalosporin G (Ceph-G) as well as 6-aminopenicillanic acid (6-APA) from penicillin G (Pen-G). In this work, immobilized PGA was utilized to catalyze the conversion of Ceph-G to 7-ADCA. Higher concentration of Ceph-G was found to show inhibition effect on the reaction. Both 7-ADCA and PAA (phenylacetic acid) were found to inhibit the activity of PGA, however, via different mechanisms. In this work, with low concentrations of Ceph-G substrate, the inhibited kinetic models were obtained by adding different concentrations of PAA or 7-ADCA. The influence from both products was discussed and compared. Both inhibition kinetic mechanisms were different in that PAA showed noncompetitive inhibition to PGA whereas 7-ADCA appeared to be of competitive inhibition.