signal transduction Models, Biological Signal Transduction article Phosphorylation Retroactivity biological model metabolism phosphatase phosphorylation Computer Simulation Drug design Enzyme Activation Enzyme Stability Kinase inhibitors Kinetics MAP Kinase Signaling System MAPK MAPK cascades Metabolic Networks and Pathways Models, Theoretical Phosphoprotein Phosphatases Phosphoric Monoester Hydrolases Protein Kinase Inhibitors Protein Kinases Signaling cascade Signaling cascades Systems Biology biochemistry computer simulation