Branched-chain amino acid aminotransferase I <p>Aminotransferases share certain mechanistic features with other pyridoxal-phosphate dependent enzymes, such as the covalent binding of the pyridoxal-phosphate group to a lysine residue. On the basis of sequence similarity, these various enzymes can be grouped [<cite idref="PUB00002195"/>] into subfamilies.</p><p>One of these, called class-IV, currently consists of proteins of about 270 to 415 amino-acid residues that share a few regions of sequence similarity. Surprisingly, the best conserved region does not include the lysine residue to which the pyridoxal-phosphate group is known to be attached, in ilvE, but is located some 40 residues at the C terminus side of the PlP-lysine.</p><p> Among the class IV aminotransferases are two phylogenetically separable groups of branched-chain amino acid aminotransferase (IlvE) (<db_xref db="EC" dbkey="2.6.1.42"/>). The last common ancestor of the two lineages appears also to have given rise to a family of D-amino acid aminotransferases (DAAT). This model represents the IlvE family more strongly similar to the DAAT family.</p>