Transamination is mediated by several types of aminotransferase enzymes. An aminotransferase may be specific for an individual amino acid, or it may be able to process any member of a group of similar ones, for example the branched-chain amino acids, which comprises valine, isoleucine, and leucine. The  two common types of aminotransferases are alanine aminotransferase (ALT) and aspartate aminotransferase (AST).