Kobayashi Jun, Yoshikane Yu, Yagi Toshiharu, Baba Seiki, Mizutani Kimihiko, Takahashi Nobuyuki, Mikami Bunzo
Laboratory of Applied Structural Biology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan.
Faculty of Agriculture and Agricultural Science Program, Graduate School of Integral Arts and Science, Kochi University, Nankoku, Kochi 783-8502, Japan.
Acta Crystallogr F Struct Biol Commun. 2014 Apr;70(Pt 4):424-32. doi: 10.1107/S2053230X14003926. Epub 2014 Mar 25.
4-Pyridoxolactonase from Mesorhizobium loti catalyzes the zinc-dependent lactone-ring hydrolysis of 4-pyridoxolactone (4PAL) to 4-pyridoxic acid (4PA) in vitamin B6 degradation pathway I. The crystal structures of 4-pyridoxolactonase and its complex with 5-pyridoxolactone (5PAL; the competitive inhibitor) were determined. The overall structure was an αβ/βα sandwich fold, and two zinc ions were coordinated. This strongly suggested that the enzyme belongs to subclass B3 of the class B β-lactamases. In the complex structure, the carbonyl group of 5PAL pointed away from the active site, revealing why it acts as a competitive inhibitor. Based on docking simulation with 4PAL, 4PA and a reaction intermediate, 4-pyridoxolactonase probably catalyzes the reaction through a subclass B2-like mechanism, not the subclass B3 mechanism.
来自百脉根中生根瘤菌的4-吡哆醇内酯酶在维生素B6降解途径I中催化4-吡哆醇内酯（4PAL）的锌依赖性内酯环水解为4-吡哆酸（4PA）。测定了4-吡哆醇内酯酶及其与5-吡哆醇内酯（5PAL；竞争性抑制剂）复合物的晶体结构。整体结构为αβ/βα三明治折叠，且有两个锌离子配位。这有力地表明该酶属于B类β-内酰胺酶的B3亚类。在复合物结构中，5PAL的羰基远离活性位点，揭示了其作为竞争性抑制剂的作用机制。基于与4PAL、4PA和反应中间体的对接模拟，4-吡哆醇内酯酶可能通过类似B2亚类的机制而非B3亚类机制催化反应。
