Crystallographic studies on apocarboxypeptidase A and the complex with glycyl-L-tyrosine.
The crystal structures of zinc-free carboxypeptidase A (apocarboxypeptidase A) and the complex of glycyl-L-tyrosine with apocarboxypeptidase A are described and compared to the corresponding structures of the zinc-containing enzyme. Only small conformational changes in the zinc ligands accompany removal of the metal. Interactions between the tyrosine residue of glycyl-L-tyrosine and apocarboxypeptidase A are similar to those observed in the complex with the holoenzyme. However, in the absence of zinc, the carbonyl oxygen of the glycyl moiety now receives a hydrogen bond from the side chain of arginine-127. Although not as yet observed, a similar shift of the carbonyl oxygen of a susceptible bond from the zinc to arginine-127 could stabilize tetrahedral intermediates generated during the hydrolysis of substrates by carboxypeptidase.
D001051:Apoenzymes / Q000378:metabolism*; D001059:Apoproteins / Q000378:metabolism*; D001120:Arginine; D002268:Carboxypeptidases / Q000378:metabolism*; D043422:Carboxypeptidases A; D004151:Dipeptides / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D014961:X-Ray Diffraction
D001051:Apoenzymes; D001059:Apoproteins; D004151:Dipeptides; D001120:Arginine; C022013:glycyltyrosine; D002268:Carboxypeptidases; D043422:Carboxypeptidases A