X-ray diffraction and nuclear magnetic resonance dispersion studies on derivatives of carboxypeptidase A.

Abstract

The isolation of crystalline carboxypeptidase A (CPA) by Anson (1937) has led to detailed studies of its structure and function in the hydrolysis either of the C-terminal amino acid of peptide substrates or of structurally similar ester substrates. Crystallographic studies have been correlated with chemical results earlier (Lipscomb, 1970; Hartsuck and Lipscomb, 1971; Quiocho and Lipscomb, 1971) and will be referred to only briefly in the first section below. However, some new crystallographic results at 2.8 Å resolution on a tetrapeptide complex with CPA, and results for binding at 6 Å resolution of products and inhibitors are given in the second section. For the first time some of these X-ray studies have a direct relationship to studies of the proton nuclear magnetic resonance spectrum as a function of frequency (nuclear magnetic resonance dispersion: NMRD) in MnCPA and some of its complexes, as discussed in the third section of this paper.