Inactivation of chymotrypsin by 5-benzyl-6-chloro-2-pyrone: 13C NMR and X-ray diffraction analyses of the inactivator-enzyme complex.
The inactivation of chymotrypsin by 5-benzyl-6-chloro-2-pyrone has been studied. Chloride analysis of the inactivated enzyme suggests that chlorine is no longer present in the complex. 13C NMR spectroscopy of chymotrypsin inactivated with 5-benzyl-6-chloro-2-pyrone-2,6-13 C2 shows the presence of two new resonances from the protein-bound inactivator. The chemical shift values of these resonances are consistent with an intact pyrone ring on the enzyme as well as the replacement of the C-6 chlorine by a different heteroatom. X-ray diffraction analysis at 1.5-A resolution of the inactivator-enzyme complex demonstrates that the gamma-oxygen of the active site serine residue (serine 195) is covalently attached to C-6 of the inactivator and that the pyrone ring is intact. The 5-benzyl group of the inactivator is bound to the enzyme in the hydrophobic specificity pocket. The conformational changes that occur in the protein as a result of complexation with the inactivator are discussed.
D001665:Binding Sites; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011714:Pyrans / Q000494:pharmacology*; D011753:Pyrones / Q000494:pharmacology*; D014961:X-Ray Diffraction / Q000379:methods
D011714:Pyrans; D011753:Pyrones; C037903:3-benzyl-6-chloro-2-pyrone; D002918:Chymotrypsin