title: Ultrasonic studies of proton-transfer reactions at the catalytic site of alpha-chymotrypsin.
abstract: Ultrasonic relaxation measurements for alpha-chymotrypsin in phosphate, sulfite and arsenate buffers exhibit a high peak of absorption at neutral pH. The analysis is based on: comparison of the relaxation measurements for the enzyme and for the zymogen and inhibited enzyme; X-ray and neutron diffraction data, and high-resolution NMR data. The ultrasonic relaxation is shown to result mainly from a proton-transfer reaction that involves the histidine at the catalytic site (His-57). The question is raised of whether the enhanced ultrasonic effect observed in the enzyme is indicative of a property that plays a part in the catalytic activity.
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007531:Isoflurophate / Q000494:pharmacology; D011522:Protons; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014465:Ultrasonics
chemical_list: D004792:Enzyme Precursors; D011522:Protons; D007531:Isoflurophate; D014108:Tosylphenylalanyl Chloromethyl Ketone; D002918:Chymotrypsin