The rate of hydrolysis of N-(phenylacetyl)glycyl-D-valine (PAGV), an acyclic penicillin G analogue, at pH 0, 1, 3, 5, 7, 9, Il, 13, and 14 has been measured at 37 degrees C and a pH-rate profile constructed. At each pH, hydrolysis of both the (phenylacetyl)glycyl amide bond and glycyl-D-valine peptide bond was monitored. At pH 3, 5, 7, 9, and 11, the hydrolysis products glycyl-D-valine and D-valine were derivatized with naphthalene-2,3-dialdehyde in the presence of cyanide; the resultant 1-cyano-2-substituted-benz[f]isoindole (CBI) derivatives, which are highly fluorescent, were then quantified using reverse-phase HPLC. The hydrolysis reactions were explicitly shown to be first-order in peptide concentration at pH 5 and 9, and all rates were shown to be independent of the buffer concentration. The rates at pH 0, 1, 13, and 14 were measured in 1 M DCl, 0.1 M DCl, 0.1 M NaOD, and 1 M NaOD, respectively, and the hydrolysis products were detected by H-1 NMR. The first-order rate constants obtained from the above reactions were fit to the general equation k = k(H2O) + k(H3O+)[H3O+] + k(OH-)[OH-] to yield the following results: for hydrolysis of the (phenylacetyl)glycyl bond, k(H2O) = (9.05 +/-6.36) x 10(-11) s(-1). k(H3O+) = (1.60 +/- 1.04) x 10(-6) M-1 s(-1,) and k(OH-) = (1.11 +/- 0.73) x 10(-6) M-1 s(-1); and for hydrolysis of the glycyl-D-valine bond, k(H2O) = (8.23 +/-4.33) x 10(-11) s(-1), k(H3O+) = (1.67 +/- 0.80) x 10(-6) M-1 s(-1), and k(OH-) = (1.16 +/- 0.56) x 10(-6) M-1 s(-1). At pH 7, the hydrolysis of both the (phenylacetyl)glycyl amide bond and glycyl-D-valine peptide bond is dominated by k(H2O). The corresponding half-lift: for (phenylacetyl)glycyl bond hydrolysis is 243 years (with a range of 143-817 years within experimental error), while that for glycyl-D-valine bond hydrolysis is 267 years (with a range of 175-564 years).