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 [1,2] into subfamilies. One of these, called class-III, currently consists of the following enzymes:

• Acetylornithine aminotransferase (EC 2.6.1.11) which catalyzes the transfer of an amino group from acetylornithine to α-ketoglutarate, yielding N-acetyl-glutamic-5-semi-aldehyde and glutamic acid.
• Ornithine aminotransferase (EC 2.6.1.13), which catalyzes the transfer of an amino group from ornithine to α-ketoglutarate, yielding glutamic-5- semi-aldehyde and glutamic acid.
• Omega-amino acid--pyruvate aminotransferase (EC 2.6.1.18), which catalyzes transamination between a variety of omega-amino acids, mono- and diamines, and pyruvate. It plays a pivotal role in omega amino acids metabolism.
• 4-aminobutyrate aminotransferase (EC 2.6.1.19) (GABA transaminase), which catalyzes the transfer of an amino group from GABA to α-ketoglutarate, yielding succinate semialdehyde and glutamic acid.
• DAPA aminotransferase (EC 2.6.1.62), a bacterial enzyme (gene bioA) which catalyzes an intermediate step in the biosynthesis of biotin, the transamination of 7-keto-8-aminopelargonic acid (7-KAP) to form 7,8- diaminopelargonic acid (DAPA).
• 2,2-dialkylglycine decarboxylase (EC 4.1.1.64), a Pseudomonas cepacia enzyme (gene dgdA) that catalyzes the decarboxylating amino transfer of 2,2-dialkylglycine and pyruvate to dialkyl ketone, alanine and carbon dioxide.
• Glutamate-1-semialdehyde aminotransferase (EC 5.4.3.8) (GSA). GSA is the enzyme involved in the second step of porphyrin biosynthesis, via the C5 pathway. It transfers the amino group on carbon 2 of glutamate-1- semialdehyde to the neighbouring carbon, to give delta-aminolevulinic acid.
• Bacillus subtilis aminotransferase yhxA.
• Bacillus subtilis aminotransferase yodT.
• Haemophilus influenzae aminotransferase HI0949.
• Caenorhabditis elegans aminotransferase T01B11.2.

The sequence around the pyridoxal-phosphate attachment site of this class of enzyme is sufficiently conserved to allow the creation of a specific pattern.

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