Functional Energetic Landscape in the Allosteric Regulation of Muscle Pyruvate Kinase. 2. Fluorescence Study
2009
Abstract
Four novel insights were uncovered. (1) ADP exhibits a dual property. Depending on the temperature, ADP can regulate RMPK activity by switching the enzyme to either the R or T state. (2) The assumption that ligand binding to RMPK is state-dependent is only correct for PEP but not Phe and ADP. (3) The effect of pH on the regulatory behavior of RMPK is partly due to the complex pattern of proton release or absorption linked to the multiple linked equilibria which govern the activity of the enzyme. (4) The R {-} T equilibrium is accompanied by a significant Delta C-p, rendering RMPK most sensitive to temperature under physiological conditions.