Hydrolysis of D,L-tryptophan isopropyl ester catalysed by beta-cyclodextrin

beta-Cyclodextrin (BCD) catalysed hydrolysis of D,L-tryptophan isopropyl ester is found to be pH dependent. The pH rate constant profiles show that the k(obs) values for the BCD catalysed reactions are higher than those of the control in the pH range 9.8 to 12.9. The reaction follows Michaelis-Menten type kinetics exhibiting substrate saturation. Michaelis-Menten treatment results in determination of K-D (0.067 M) and k(cat) (0.015 M(-1) min(-1)). A k(cat)/ k(un) values of 0.94 has been determined. Tryptophan, the hydrolysis product formed exhibited enantiometric excess of 7.9 to 18.4% of the (-) antipode in reactions catalysed by BCD, heptakis-2,6-di-O-methyl-beta-cyclodextrin (DM-BCD), BCD-epiclorohydrin polymer (BCD-polymer) and a 1:1 complex of Cu(II)-beta-cyclodextrin (Cu(II)-BCD).