Inhibition of α-Chymotrypsin by Diethyl Ether and Certain Alcohols: a New Type of Competitive Inhibition

Abstract

The enzyme used was a salt-free, twice crystallized sample of cu-chymotrypsin supplied by the Sigma Chemical Company. The methyl ester of hydrocinnamic acid (3-phenylpropionic acid) was prepared by refluxing 5 g of the acid with 750 ml of Fisher’s chemically pure methanol and a few drops of concentrated sulfuric acid as a catalyst. The reaction mixture was refluxed for 2 days. The excess of methanol was evaporated under reduced pressure, and the residue was extracted with ether. The ether was washed with 10 100 ml portions of 5% sodium bicarbonate. The ether was evaporated under reduced pressure, and the ester was distilled under reduced pressure, the middle 30% being collected. The boiling poin$ was 236-237” at atmospheric pressure. The methyl hippurate was prepared by heating a mixture of hippuric acid in the presence of a large excess of methanol to 190” under an atmosphere of hydrogen at approximately 2500 pounds per square inch (3). After subsequent purification, the melting point was 82-83”. The concentration of the enzyme was approximately 1