School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daehak-ro 80, Buk-ku, Daegu, 702-701, Republic of Korea; KNU Institute for Microorganisms, Kyungpook National University, Daegu, 41566, Republic of Korea.
School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daehak-ro 80, Buk-ku, Daegu, 702-701, Republic of Korea; KNU Institute for Microorganisms, Kyungpook National University, Daegu, 41566, Republic of Korea.
Biochem Biophys Res Commun. 2019 Feb 12;509(3):833-838. doi: 10.1016/j.bbrc.2019.01.018. Epub 2019 Jan 10.
Metallosphaera sedula is a thermoacidophilic autotrophic archaeon and known to utilize the 3-hydroxypropionate/4-hydroxybutyrate cycle (3-HP/4-HB cycle) as a carbon fixation pathway. The 3-HP/4-HB cycle in M. sedula is associated with central metabolism, and malate dehydrogenase (MDH) is an enzyme involved in the central metabolism that converts malate to oxaloacetate. To elucidate the enzymatic properties of MDH from M. sedula (MsMDH), we determined the crystal structure of MsMDH as a complex with NAD and a ternary complex with malate and NAD. Based on its complex structures and biochemical experiments, we observed that MsMDH can utilize both NAD and NADP as a cofactor. In addition, we revealed that MsMDH shows a conformational change at the active site upon substrate binding. Based on the comparison with other MDHs, we revealed that MsMDH was distinguished from general MDHs due to a Lys80 residue, and this difference is likely to influence the unique cofactor specificity of MsMDH.
喜温硫杆菌是一种嗜热嗜酸的自养古菌，已知其利用 3-羟基丙酸/4-羟基丁酸循环（3-HP/4-HB 循环）作为碳固定途径。喜温硫杆菌中的 3-HP/4-HB 循环与中心代谢有关，而苹果酸脱氢酶（MDH）是一种参与中心代谢的酶，可将苹果酸转化为草酰乙酸。为了阐明来自喜温硫杆菌（MsMDH）的 MDH 的酶学性质，我们确定了 MsMDH 与 NAD 形成复合物以及与苹果酸和 NAD 形成三元复合物的晶体结构。基于其复合物结构和生化实验，我们观察到 MsMDH 可以同时利用 NAD 和 NADP 作为辅助因子。此外，我们揭示了 MsMDH 在底物结合时在活性位点发生构象变化。通过与其他 MDHs 的比较，我们发现由于存在一个赖氨酸 80 残基，MsMDH 与一般的 MDHs 不同，这种差异可能影响 MsMDH 独特的辅酶特异性。
