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

摘要

Penicillin G acylase(PGA)is an important enzyme in beta-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.