1ay5
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AROMATIC AMINO ACID AMINOTRANSFERASE COMPLEX WITH MALEATE
OverviewOverview
Aminotransferase reversibly catalyzes the transamination reaction by a, ping-pong bi-bi mechanism with pyridoxal 5'-phosphate (PLP) as a cofactor., Various kinds of aminotransferases developing into catalysts for, particular substrates have been reported. Among the aminotransferases, aromatic amino acid aminotransferase (EC 2.6.1. 57) catalyzes the, transamination reaction with both acidic substrates and aromatic, substrates. To elucidate the multiple substrate recognition mechanism, we, determined the crystal structures of aromatic amino acid aminotransferase, from Paracoccus denitrificans (pdAroAT): unliganded pdAroAT, pdAroAT in a, complex with maleate as an acidic substrate analog, and pdAroAT in a, complex with 3-phenylpropionate as an aromatic substrate analog at 2.33 A, 2. 50 A and 2.30 A resolution, respectively.The pdAroAT molecule is a, homo-dimer. Each subunit has 394 amino acids and one PLP and is divided, into small and large domains. The overall structure of pdAroAT is, essentially identical to that of aspartate aminotransferase (AspAT) which, catalyzes the transamination reaction with only an acidic amino acid. On, binding the acidic substrate analog, arginine 292 and 386 form end-on salt, bridges with carboxylates of the analog. Furthermore, binding of the, substrate induces the domain movement to close the active site. The, recognition mechanism for the acidic substrate analog in pdAroAT is, identical to that observed in AspAT. Binding of the aromatic substrate, analog causes reorientation of the side-chain of the residues, lysine 16, asparagine 142, arginine 292* and serine 296*, and changes in the position, of water molecules in the active site to form a new hydrogen bond network, in contrast to the active site structure of pdAroAT in the complex with an, acidic substrate analog. Consequently, the rearrangement of the hydrogen, bond network can form recognition sites for both acidic and aromatic, side-chains of the substrate without a conformational change in the, backbone structure in pdAroAT.
About this StructureAbout this Structure
1AY5 is a Single protein structure of sequence from Paracoccus denitrificans with PLP and MAE as ligands. Active as Aromatic-amino-acid transaminase, with EC number 2.6.1.57 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of Paracoccus denitrificans aromatic amino acid aminotransferase: a substrate recognition site constructed by rearrangement of hydrogen bond network., Okamoto A, Nakai Y, Hayashi H, Hirotsu K, Kagamiyama H, J Mol Biol. 1998 Jul 17;280(3):443-61. PMID:9665848
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