Length of the acyl carbonyl bond in acyl-serine proteases correlates with reactivity.

摘要: Resonance Raman (RR) spectroscopy has been used to obtain the vibrational spectrum of acyl carbonyl group in a series acylchymotrypsins and acylsubtilisins at pH optimum hydrolysis. The acyl-enzymes, which utilize arylacryloyl groups, include three oxyanion hole mutants subtilisin BPN', Asn155Leu, Asn155Gln, Asn155Arg, encompass 500-fold range deacylation rate constants. For each acyl-enzyme RR band identified arises from population groups undergoing nucleophilic attack active site. As (k3) increases through stretching (vC = O) is observed shift lower frequency, indicating an increase single bond character reactive group. Experiments involving BPN' indicate that vC O frequency results stronger hydrogen bonding hole. A plot log k3 against linear over investigated, demonstrating changes correlate with free energy activation for reaction. By use empirical correlation between length (rC it estimated rC by 0.015 as acyl-enzymes. This change about 7% expected going formal C double C-O tetrahedral intermediate deacylation. data also allow us estimate needed extend along its axis be 950 kJ mol-1 A-1.