ABSTRACT
Enzymes are one of the essential components of all living systems. These macromolecules have a key role in catalyzing the chemical transformations that occur in all cell metabolism. The nature and specificity of their catalytic activity is primarily due to the three-dimensional structure of the folded protein, which is determined by the sequence of the amino acids that make up the enzyme. The activity of globular proteins may be regulated by one or more small molecules, which cause small conformational changes in the protein structure. Catalytic activity may depend on the action of these non-protein components (known as cofactors) associated with the protein. If the cofactor is an organic molecule, it is referred to as a coenzyme. The catalytically inactive enzyme (without cofactor) is termed an apoenzyme; when coenzyme or metal ion is added, the active enzyme is then termed a holoenzyme. Many cofactors are tightly bound to the enzyme and cannot be easily removed; they are then referred to as prosthetic groups.
