Optimal temperature and pH also increase rates of enzymatic reaction. As temperature rises, there is increase in enzyme activity. A change in pH alters ionization of side chains, eventually resulting in denaturation. Other enzymes called phosphatases remove phosphate groups from enzymes. Phosphorylation and dephosphorylation regulate protein synthesis, cell division, activity of motor molecules, nuclear envelope breakdown, and development.
Inhibition is common means by which cells regulate enzyme activity.
In competitive inhibition, another molecule is similar to enzyme's substrate, competes with true substrate for enzyme's active site, resulting in decreased product formation. In noncompetitive inhibition, a molecule binds to allosteric site, a site other than active site, hereby changing the three-dimensional structure of enzyme and ability to bind to its substrate. Many enzymes require an inorganic ion or nonprotein cofactor to function. Pathways of photosynthesis and aerobic respiration transform one form of energy into another. Without a constant input of solar energy, life could not exist.