InterPro domain: IPR001544

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 ] into subfamilies.

This entry represents a subfamily of aminotransferases, called class-IV, with 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 pyridoxal-phosphate-lysine. The D-amino acid transferases (D-AAT), which are among the members of this entry, are required by bacteria to catalyse the synthesis of D-glutamic acid and D-alanine, which are essential constituents of bacterial cell wall and are the building block for other D-amino acids. Despite the difference in the structure of the substrates, D-AATs and L-ATTs have strong similarity [ 2 , 3 ].

This group also includes transaminase htyB from Aspergillus rugulosus , which is one of the enzymes required for the biosynthesis of the antifungal agent echinocandin B. HtyB catalyses the production of L-homotyrosine from the intermediate 2-oxo-4-(4-hydroxybenzyl)butanoic acid [ 4 ]. Also included in this group is branched-chain amino acid aminotransferase gloG from the yeast Glarea lozoyensis , which is required for biosynthesis of the mycotoxin pneumocandin, also a lipohexapeptide of the echinocandin family [ 5 ].

1. Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme. J. Bacteriol. 174, 5317-23
2. Crystal structure of a D-amino acid aminotransferase: how the protein controls stereoselectivity. Biochemistry 34, 9661-9
3. Three-dimensional structure of Escherichia coli branched-chain amino acid aminotransferase at 2.5 A resolution. J. Biochem. 121, 637-41
4. Identification and characterization of the echinocandin B biosynthetic gene cluster from Emericella rugulosa NRRL 11440. J. Am. Chem. Soc. 134, 16781-90
5. Structural diversity in echinocandin biosynthesis: the impact of oxidation steps and approaches toward an evolutionary explanation. Z. Naturforsch., C, J. Biosci. 72, 1-20