ABSTRACT
Enzymes are involved in our lives in various ways and are essential to maintain our body. Cellular components are kept in almost constant concentrations, and pH of our body fluid and our body temperature are also maintained at almost constant values. The phenomena are called homeostasis. Enzymes maintain homeostasis, since they catalyze and regulate reactions in cells. Enzyme activities change various conditions: pH, temperature, ligand-binding, and covalent modifications. The amount of enzyme also regulates the reactions in cells. This chapter focuses on the control of enzymatic activities by non-covalent ligand binding and the covalent modification of enzyme.
