Effects of Cyclodextrins on Chymotrypsin Action

Inhibition by cyclodextrins ofchymotrypsin-catalysed hydrolysis of N-acetyl-L-tyrosineethyl ester (ATEE) and of N-succinyl-L-phenylalaninep-nitroanilide (SUPHEPA) was measured. Rates ofproteolysis are reduced by a factor of three tofour by a four-molar ratio of cyclodextrin tosubstrate, except for -cyclodextrin andSUPHEPA where the rate reduction is much less.The kinetics of inhibition, as well as NMR andUV measurements, were used to measureassociation constants between the cyclodextrinsand substrates. Agreement between these methodsconfirmed that inhibition by cyclodextrins isdue to steric effects at the substrate, ratherthan direct interaction with the enzyme.