Peptide Bond Cleavage on Trypsin-Trypsin Inhibitor Complex Formation

Modification of Amino Groups in Inhibitors of Proteolytic Enzymes*

“…The results of studies in this laboratory as well as others (Fraenkel-Conrat et al, 1952;Finkenstadt and Laskowski, 1965; Ozawa and Laskowski, 1966) can be considered as showing that either lysines or arginines are required for the activities of protein trypsin inhibitors. The kinetic analyses in the present study indicate that either one or two of the "fast"-reacting amino groups, depending on the inhibitor, are essential for activity in four of the trypsin inhibitors studied.…”

Protein inhibitors of proteolytic enzymes

“…By analogy to nonenzymatic acyl-transfer reactions, tetrahedral structures are presumed to be intermediates in normal peptide hydrolyses catalyzed by serine proteinases, but have never been directly observed, and are presumed to exist only in low steady-state amounts. They are extremely unstable, approaching the transition-state energy for enzyme acylation, typically [16][17][18][19] keal/mol less stable than the concovalent Michaelis-Menten-type complexes from which they are derived.57'58 Such species, to exist in detectable amounts, would require specific and highly effective stabilization. Rather than accounting for the stability of these enzyme-inhibitor complexes, the existence of such a structure would more likely decrease their stability.…”

Enzymic replacement of the arginyl by a lysyl residue in the reactive site of soybean trypsin inhibitor

“…Arg( 64) is easily removed from the modified inhibitor by short treatment with Cpase B (reaction 2, Figure 1); the product, des-64-arginine-modified inhibitor (hereafter, desarginine inhibitor or Sc*), appears to be devoid of inhibitory activity and can be isolated in large quantities. Virgin inhibitor is not affected by carboxypeptidase B treatment (Finkenstadt and Laskowski, 1965; Ozawa and Laskowski, 1966;Niekamp etal., 1969).…”