THE LOCAL DYNAMICS OF THE ACTIVE-SITE REGION OF GLYCOGEN-PHOSPHORYLASE-B

The parameters characterizing the quenching of fluorescence emitted by the coenzyme (pyridoxal-5'-phosphate) of phosphorylase b (EC 2.4.1.1) by anions are good indicators of conformational/dynamic changes at th e active center. Reinvestigation of this quenching process resulted in a non-linear Stem-Volmer plot. This non-linearity is described by a s imple kinetic model which assumes two parallel processes, one represen ted by bound and the second by free quencher molecules. Analysis of se parate parts of the nonlinear Stem-Volmer plot results in the values o f rate constants for the bound and free quencher molecules as well as the value of dissociation constant of the anions. (C) 1995 Academic Pr ess, Inc.