Scheule R K, Han S L, Van Wart H E, Vallee B L, Scheraga H A
Biochemistry. 1981 Mar 31;20(7):1778-84. doi: 10.1021/bi00510a011.
The interaction of inhibitors with the active site of arsanilazocarboxypeptidase A has been investigated by means of resonance Raman spectroscopy. The resonance Raman bands of the active-site azotyrosine-248 residue have been shown previously to be sensitive to its state of ionization and its interactions with nearby groups. In particular, the azophenol form of azotyrosine-248 can adopt two different coexisting conformations that differ with respect to the presence or absence of an intramolecular hydrogen bond between the phenolic proton and a nitrogen atom of the azo group. Each of these conformations exhibits characteristic vNN and v phi N azo stretching frequencies. The relative concentrations of these two forms, revealed by resonance Raman spectroscopy, are a sensitive probe of the hydrogen bond accepting ability of the local environment. The present study shows that the binding of L-benzylsuccinate, phenylacetate, L-phenyllactate, and beta-phenylpropionate markedly perturbs the distribution of the intra- and intermolecularly hydrogen-bonded forms of azotyrosine-248 in water. In contrast, glycyl-L-tyrosine and L-phenylalanine leave this distribution unperturbed. These results, taken jointly with other data on inhibitor binding, serve to identify common binding sites for groups of inhibitors and result in plausible suggestions concerning the interactions between azotyrosine-248 and these inhibitors that lead to binding.
