The hydrolysis of 2-pheny1-oxazolin-5-one and 4,4-dimethyl-2-phenyl-oxazolin-5-one is catalysed by hydrogen and hydroxide ions . By carrying out the hydrolysis of 2-phenyl-oxazolin-5-one in oxygen-18 enriched water, it has been shown that under both acidic and basic conditions, the reaction proceeds at the carbonyl carbon atom.
Kinetic evidence indicates that p-nitrophenyl hippurate and benzoy1-D,L-alanine p-nitrophenyl ester in imidazole buffers form an acy1-imidazole as an intermediate in hydrolysis, while benzoylaminoisobutyric acid p-nitrophenyl ester does not. The kinetics of hydrolysis of these three esters under a variety of conditions provides evidence against the involvement of either acy1-imidazoles or oxazolin-5-ones in chymotryptic catalysis.
A stable acy1-chymotrypsin has been prepared which contains an ionizable chromophore in the acyl group. The behaviour of this group suggests that the enzyme active site resembles a medium of low dielectric constant. It has been shown that the alkylating agent a-bromoacetophenone irreversibly inhibits chicken liver carboxylesterase by reaction with a single histidine residue. This residue is located at or near the active site. The effect of tetranitromethane on several esterases has been examined.
Oxygen-18 tracer techniques have been used to explore the mechanism of the rearrangement of o-nitrotoluene to anthranilic acid in aqueous alkali. It was found that one of the oxygen atoms from the nitro group was transferred to the carboxyl group of the product during the rearrangement. An enzyme catalysing the same conversion has been isolated and partially characterized.
A preliminary publication describing the work on the hydrolysis of N-acylamino acid esters has been published: J. de Jersey, P. Willadsen, B. Zerner, Biochemistry 8, 1959 (1969).