To assess the relative proficiencies of enzymes that catalyze the hydrolysis of internal and C- terminal peptide bonds, the rates of the corresponding nonenzymatic reactions were examined at elevated temperatures in sealed quartz tubes, yielding linear Arrhenius plots. The results indicate that in neutral solution at 25° C, peptide bonds are hydrolyzed with half- times of approximately 500 years for the C-terminal bond of acetylglycylglycine, 600 years ...