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 the active center. Reinvestigation of this quenching process resulted in a non-linear Stern-Volmer plot. This non-linearity is described by a simple kinetic model which assumes two parallel processes, one represented by bound and the second by free quencher molecules. Analysis of separate parts of the non-linear Stern-Volmer plot results in the values of rate constants for the bound and free quencher molecules as well as the value of dissociation constant of the anions.