Thermodynamics of Hydrolysis of Peptide Bonds

Chicken ovomucoid: determination of its amino acid sequence, determination of the trypsin reactive site, and preparation of all three of its domains

“…The values at different pHs are given in Figure 3B. It is seen there that the data can be fitted very well to the Dobry, Fruton, and Sturtevant (Dobry et al, 1952) (2) with the parameters given in the legend to Figure 3B. In the simplest possible interpretation, p is the pK of the carboxyl group of Arg89 (P, residue) and pK2 is the pK of the alkylammonium group of Ala90 in OMCHI*.…”

Enzymic resynthesis of the hydrolyzed peptide bond(s) in ribonuclease S

“…The more serious objections that can be raised are that 4.3% synthesis is too small to be believable experimentally and even more importantly that insufficient proof of attainment of equilibrium was provided.3 These objections are largely but not completely answered by the facts that the ribonuclease Aand ribonuclease S-subtilisin incubation curves come into coincidence at the point of maximal synthesis, that the values of the maximal synthesis obtained in various glycerol solutions smoothly depend upon the added glycerol concentration, and that the effect of glycerol upon these maximal synthesis values is quantitatively similar, although not identical, to that of the effect of glycerol upon Ksyn°o f benzyloxycarbonyltryptophanylglycinamide and of the reactive site in soybean trypsin inhibitor (Kunitz) (Homandberg et al, 1978). Furthermore, the pH dependence of the maximal synthesis value in 90% glycerol is the simplest possible predicted for peptide bond hydrolysis equilibria (Dobry et al, 1952). Thus, treating maximal synthesis values obtained in various glycerol solutions and at various pH values as if they were equilibrium amounts of synthesis introduces no inconsistencies.…”

Thermodynamics and kinetics of the hydrolysis of the reactive-site peptide bond in pancreatic trypsin inhibitor (Kunitz) by Dermasterias imbricata trypsin 1

“…The two values are clearly different, however, within the limits of what we expect to be our experimental error in Kbyd (roughly ±0.04). While we were unable to measure Alhyd at pH 5, we regard such a sudden deviation from the equation of Dobry et al (1952), eq 4, as highly unlikely. The cause of the discrepancy arises either as a result of the different ionic strengths used in the experiments-quite low in the experiment of Tschesche & Kupfer (1976) and high in ours-or to some systematic errors arising from the extremely long incubation times (on the order of 1 year) used by Tschesche & Kupfer (1976).…”