Crystallographic study of steps along the reaction pathway of D-amino acid aminotransferase
Crystallographic study of steps along the reaction pathway of D-amino acid aminotransferase
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DOI：
10.1021/bi972884d
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发表时间：
1998-04-07
期刊：
影响因子：
2.9
通讯作者：
Ringe, D
中科院分区：
文献类型：
--
作者：
Peisach, D;Chipman, DM;Ringe, D
从芽孢杆菌sp. m -1中分离出两种形式的d -氨基酸转氨酶（D-aAT）的三维结构：磷酸吡哆醛（PLP）形式和与外部醛胺的还原类似物N-（5'-磷酸吡哆醇基）- d -丙氨酸（PPDA）的配合物。再加上之前报道的磷酸吡啶多胺酶[Sugio et al. (1995) Biochemistry, 34,9661]，这些结构使我们能够从结构上描述酶反应的途径。该酶对d -氨基酸的立体特异性的主要决定因素是一组三个残基（Tyr30， Arg98和His100，后两个由邻近的亚基贡献）与底物α -羧基形成四个氢键。支链l -氨基酸氨基转移酶的同源残基（具有相似的折叠）被疏水基取代可以解释其相反的立体特异性。与l -天冬氨酸转氨酶（L-AspAT）一样，D-aAT的辅因子在反应过程中（围绕其磷酸基团和N1为支点）向催化赖氨酸145和蛋白面倾斜。与L-AspAT不同，D-aAT在反应过程中没有其他明显的构象变化。
The 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.