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CRYSTALLOGRAPHIC STRUCTURE OF D-AMINO ACID AMINOTRANSFERASE INACTIVATED BY PYRIDOXYL-D-ALANINECRYSTALLOGRAPHIC STRUCTURE OF D-AMINO ACID AMINOTRANSFERASE INACTIVATED BY PYRIDOXYL-D-ALANINE
Structural highlights
FunctionDAAA_BACYM Acts on the D-isomers of alanine, leucine, aspartate, glutamate, aminobutyrate, norvaline and asparagine. The enzyme transfers an amino group from a substrate D-amino acid to the pyridoxal phosphate cofactor to form pyridoxamine and an alpha-keto acid in the first half-reaction. The second-half reaction is the reverse of the first, transferring the amino group from the pyridoxamine to a second alpha-keto acid to form the product D-amino acid via a ping-pong mechanism. This is an important process in the formation of D-alanine and D-glutamate, which are essential bacterial cell wall components.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe three-dimensional structures of two forms of the D-amino acid aminotransferase (D-aAT) from Bacillus sp. YM-1 have been determined crystallographically: the pyridoxal phosphate (PLP) form and a complex with the reduced analogue of the external aldimine, N-(5'-phosphopyridoxyl)-d-alanine (PPDA). Together with the previously reported pyridoxamine phosphate form of the enzyme [Sugio et al. (1995) Biochemistry 34, 9661], these structures allow us to describe the pathway of the enzymatic reaction in structural terms. A major determinant of the enzyme's stereospecificity for D-amino acids is a group of three residues (Tyr30, Arg98, and His100, with the latter two contributed by the neighboring subunit) forming four hydrogen bonds to the substrate alpha-carboxyl group. The replacement by hydrophobic groups of the homologous residues of the branched chain L-amino acid aminotransferase (which has a similar fold) could explain its opposite stereospecificity. As in L-aspartate aminotransferase (L-AspAT), the cofactor in D-aAT tilts (around its phosphate group and N1 as pivots) away from the catalytic lysine 145 and the protein face in the course of the reaction. Unlike L-AspAT, D-aAT shows no other significant conformational changes during the reaction. Crystallographic study of steps along the reaction pathway of D-amino acid aminotransferase.,Peisach D, Chipman DM, Van Ophem PW, Manning JM, Ringe D Biochemistry. 1998 Apr 7;37(14):4958-67. PMID:9538014[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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