Formation of a covalent intermediate between α-chymotrypsin and the B-chain of insulin during enzyme-catalyzed hydrolysis

Direct linkage of EGF to its receptor: Characterization and biological relevance

“…We subsequently became aware that EGF binding to the EGF receptor persists in detergent solution [42], even though at that time there were reports in the literature that EGF binding activity was inactivated by detergent treatment [ 14, 381. There is precedent in the literature for the formation of a covalent complex between two reversibly bound proteins. Chymotrypsin forms significant amounts of covalent intermediates with its substrates, including the insulin B chain, during the initial burst of its catalytic activity [39]. Kunitz soybean trypsin inhibitor and trypsin also form a covalent adduct 1401.…”

Interaction of the Kunitz soybean trypsin inhibitor with bovine trypsin. Evidence for an acyl-enzyme intermediate during complexation

“…The postulated acyl-enzymc intermediate in which the acyl moiety of the substrate is covalently linked to the active site of the enzyme has actually been isolated in the case of the interaction of chymotrypsin with />-niirophenyl acetate (Balls and Aldrich, 1955;Oosterbaan and van Adrichcm, 1958;Wahlby, 1970) and more recently with the j3 chain of insulin (Dahlquist and Wahlby, 1975). The isolation of an acyl-enzyme intermediate involving macromolecular substrates, however, has proved much more difficult because of their low concentration and marked instability.…”