Productive and nonproductive substrate binding in enzyme mimics

Abstract

Hydrolytic activity of molecularly imprinted polymeric mimics of chymotrypsin was evaluated against N-acetyl tyrosyl para nitrophenyl ester and N-benzoyl tyrosyl para nitrophenyl ester, respectively. The mimic grafted on hydrophilic support exhibited high k_cat and high K_m values for N-acetyl tyrosyl para nitrophenyl ester. But, for N-benzoyl tyrosyl para nitrophenyl ester, the mimic exhibited low k_cat as well as low K_m values, consistent with the nonproductive binding exhibited by natural chymotrypsin for hydrophobic substrate. The same mimic when grafted on hydrophobic support exhibited trends consistent with Michaelis-Menten kinetics and also higher catalytic activity than that exhibited by the mimic on hydrophilic support. Thus in the case of mimics nonproductive substrate binding could be eliminated by the choice of appropriate support. This helped to enhance the mimic activity towards a specific substrate. This discretion is not available in the case of native enzyme.