On the reaction of diazoacetyl compounds with pepsin.

摘要: Abstract Previous studies have shown that diazoacetyl--dl-norleucine methyl ester inactivates pepsin, Cu(II) greatly facilitates the reaction, and in presence of substitution occurs specifically at carboxyl group an aspartic acid residue enzyme. The present experiments were designed to establish reasons for speed specificity reaction role metal ion. Ag(I) proves be as effective promoting whereas Cd(II), Co(II), Pb(II), Zn(II) are not effective. Au(III) pepsin absence a diazo compound. If compound mixed prior addition rate inactivation is increased, suggesting reactive complex formed. pH optimum 5.5 5.8, with it 4.9. reduced about 5.0. diazotized inhibitor need substrate analogue, diazoacetylglycine ethyl serves well norleucine derivative. Diazoacetic also rapidly Cu(II), but more than 1 eq reagent incorporated. Although rates prepared from pepsinogen commercial similar, stoichiometry not. More diazoacetyl incorporated into which known heterogeneous, pepsinogen. It suggested copper-complexed carbene species. This hypothesis supported by finding dimethylsulfonium phenacylide, form such complex, Cu(II). Reaction thought occur protonated determined proximity ionized orient positively charged molecule. proposed mechanism compatible or near active site two groups markedly different pK values. One these has higher either previous kinetic implicated activity thus appears there may least three involved pepsin.