many biochemical effects, such as changing its conformation to alter its binding to a specific ligand to increase or reduce its activity. Phosphorylation and dephosphorylation can be used on all types of substrates, such as structural proteins, enzymes, membrane channels, signaling molecules, and other kinases and phosphatases. The sum of these processes is referred to as phosphoregulation. The deregulation of phosphorylation can lead to disease. Post-translational modification During the synthesis of proteins, polypeptide chains, which are created by ribosomes translating mRNA, must be processed before assuming a mature conformation. The dephosphorylation of proteins is a mechanism for modifying behavior of a protein, often by activating or inactivating an enzyme. Components of the protein synthesis apparatus also undergo phosphorylation and dephosphorylation and thus regulate the rates of protein synthesis. As part of posttranslational modifications, phosphate groups may be removed from serine, threonine, or tyrosine. As such, pathways of intracellular signal transduction depend on sequential phosphorylation and dephosphorylation of a wide variety of proteins. ATP ATP4− + H2O ⟶ ADP3− + HPO42− + H+ Adenosine triphosphate, or ATP, acts as a free energy "currency" in all living organisms. In a spontaneous dephosphorylation reaction 30.5 kJ/mol is released, which is harnessed to drive cellular reactions. Overall, nonspontaneous reactions coupled to the dephosphorylation of ATP are spontaneous, due to the negative free energy change of the coupled reaction. This is important in driving oxidative phosphorylation. ATP is dephosphorylated to ADP and inorganic phosphate. On the cellular level, the dephosphorylation of ATPases determines the flow of ions into and out of the cell. Proton pump inhibitors are a class of drug that acts directly on ATPases of the gastrointestinal tract. Dephosphorylation in other reactions Other molecules besides ATP undergo dephosphorylation as part of other biological systems. Different compounds produce different free energy changes as a result of dephosphorylation. Psilocybin also relies on dephosphorylation to be metabolized into psilocin and further eliminated. No information on psilocybin's effect on the change in free energy is currently available. Importance of Dephosphorylation in Photosystem II The first protein complex of the photosynthesis component light-dependent reactions is referred to as photosystem II. The complex utilizes an enzyme to capture photons of light, providing the greater photosynthesis process with all of the electrons needed to produce ATP. Photosystem II is particularly temperature sensitive, and desphosphorylation has been implicated as a driver of plasticity in responding to varied temperature. Accelerated protein dephosphorylation