DEACYLATION RATES OF SEVERAL TRIFLUOROMETHYL-SUBSTITUTED ACYLCHYMOTRYPSINS

The rates of deacylation of 3-trifluoromethylbutyryl-, 4-trifluoromethylbutyryl-, 5-trifluoromethylvaleryl-, and 8-trifluoromethyloctanoyl acylchymotrypsins have been determined at pH 4.0 and 7.28. After approximate corrections for the inductive and steric effects of the trifluoromethyl group, it was found that the deacylation rates for the firstmentioned acyl enzyme are not unusual when compared with the corresponding unfluorinated alkyl derivative. The 4- trifluoromethylbutyryl compound is about nine times more reactive than anticipated from the behavior of the corresponding unsubstituted derivative while the last two materials react at about one-half the expected rate. It is suggested that these rate variations may, in part, arise from perturbations in the relative populations of various conformations of the acyl group that result from introduction of fluorine atoms into the alkyl chain. © 1969, American Chemical Society. All rights reserved.