MEASUREMENT OF THE INDIVIDUAL PK(A) VALUES OF ACIDIC RESIDUES OF HEN AND TURKEY LYSOZYMES BY 2-DIMENSIONAL H-1-NMR

The pH dependence of the two-dimensional H-1 nuclear magnetic resonanc e spectra of hen and turkey egg-white lysozymes has been recorded over the pH range 1-7. By monitoring the chemical shifts of the resonances of the various protons of ionizable residues, individual pK, values f or the acidic residues have been determined for both proteins. The pK( a) values are displaced, with the exception of those of the residues i n the active site cleft, by an average of 1 unit to low pH compared to model compounds.