Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
Biosci Rep. 2011 Oct;31(5):323-32. doi: 10.1042/BSR20100117.
Mammalian mAspAT (mitochondrial aspartate aminotransferase) is recently reported to have KAT (kynurenine aminotransferase) activity and plays a role in the biosynthesis of KYNA (kynurenic acid) in rat, mouse and human brains. This study concerns the biochemical and structural characterization of mouse mAspAT. In this study, mouse mAspAT cDNA was amplified from mouse brain first stand cDNA and its recombinant protein was expressed in an Escherichia coli expression system. Sixteen oxo acids were tested for the co-substrate specificity of mouse mAspAT and 14 of them were shown to be capable of serving as co-substrates for the enzyme. Structural analysis of mAspAT by macromolecular crystallography revealed that the cofactor-binding residues of mAspAT are similar to those of other KATs. The substrate-binding residues of mAspAT are slightly different from those of other KATs. Our results provide a biochemical and structural basis towards understanding the overall physiological role of mAspAT in vivo and insight into controlling the levels of endogenous KYNA through modulation of the enzyme in the mouse brain.
哺乳动物 mAspAT（线粒体天冬氨酸氨基转移酶）最近被报道具有 KAT（犬尿氨酸氨基转移酶）活性，并在大鼠、小鼠和人脑中 KYNA（犬尿氨酸）的生物合成中发挥作用。本研究关注的是小鼠 mAspAT 的生化和结构特征。在这项研究中，首先从鼠脑的第一链 cDNA 中扩增了小鼠 mAspAT cDNA，并在大肠杆菌表达系统中表达了其重组蛋白。测试了 16 种酮酸作为小鼠 mAspAT 的辅助底物特异性，其中 14 种能够作为酶的辅助底物。通过大分子晶体学对 mAspAT 的结构分析表明，mAspAT 的辅酶结合残基与其他 KATs 的相似。mAspAT 的底物结合残基与其他 KATs 的略有不同。我们的研究结果为理解 mAspAT 在体内的整体生理作用提供了生化和结构基础，并为通过调节小鼠大脑中的酶来控制内源性 KYNA 的水平提供了深入了解。
