E

Epitope denotes the region of an antigen that is recognized and bound by an antibody. The region of an antibody that binds to the epitope is called paratope.

Enzymes are proteins that accelerate a specific chemical reaction, i. e. they act as biological catalysts. In general, they are relatively large polypeptides, made of one or several chains of amino acids that fold into a specific 3D structure. They are specific to their substrates and catalyzed reaction type. Virtually any process in a cell is catalyzed and therefore regulated by an enzyme. Prominent examples include digestive enzymes that chop food into suitable nutrients, enzymes in the citric acid cycle that provide energy to cells, and enzymes that regulate gene expression.