Department of Applied Biological Science, Kagawa University, Miki-cho, Kita-gun, Japan.
Arch Biochem Biophys. 2010 Oct 15;502(2):81-8. doi: 10.1016/j.abb.2010.08.002. Epub 2010 Aug 6.
We identified a gene encoding a soluble quinoprotein glucose dehydrogenase homologue in the hyperthermophilic archaeon Pyrobaculum aerophilum. The gene was overexpressed in Escherichia coli, after which its product was purified and characterized. The enzyme was extremely thermostable, and the activity of the pyrroloquinoline quinone (PQQ)-bound holoenzyme was not lost after incubation at 100 degrees C for 10 min. The crystal structure of the enzyme was determined in both the apoform and as the PQQ-bound holoenzyme. The overall fold of the P. aerophilum enzyme showed significant similarity to that of soluble quinoprotein aldose sugar dehydrogenase (Asd) from E. coli. However, clear topological differences were observed in the two long loops around the PQQ-binding sites of the two enzymes. Structural comparison revealed that the hyperthermostability of the P. aerophilum enzyme is likely attributable to the presence of an extensive aromatic pair network located around a beta-sheet involving N- and C-terminal beta-strands.
我们在嗜热古菌 Aeropyrum pernix 中鉴定到一个编码可溶性醌蛋白葡萄糖脱氢酶同源物的基因。该基因在大肠杆菌中过表达，随后对其产物进行了纯化和表征。该酶具有极强的热稳定性，在 100°C 下孵育 10 分钟后，结合吡咯喹啉醌（PQQ）的全酶活性并未丧失。该酶的晶体结构在apo 形式和 PQQ 结合的全酶形式下均已确定。酶的整体折叠结构与大肠杆菌中的可溶性醌蛋白醛糖脱氢酶（Asd）表现出显著的相似性。然而，在两个酶的 PQQ 结合位点周围的两个长环中观察到明显的拓扑差异。结构比较表明， Aeropyrum pernix 酶的高热稳定性可能归因于存在广泛的芳香对网络，该网络位于涉及 N-和 C-末端β-链的β-片层周围。
