Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 9-1, Bunkyo 3-Chome, Fukui 910-8507, Japan.
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
J Biochem. 2018 Apr 1;163(4):321-328. doi: 10.1093/jb/mvy004.
Hetero-trimeric aldehyde oxidases of bacterial origin, which use O2 to catalyse the oxidation of various aldehydes but not those of aromatic N-heterocycles, belong to the xanthine oxidase family. In the present study, the crystal structure of a recombinant aldehyde oxidase from Methylobacillus sp. KY4400 (Mb-AOX) was determined at 2.5 Å resolution. The structures of its subunits resemble those of the corresponding subunits or domains of other structurally characterised enzymes belonging to the family, and include a [4Fe-4 S] cluster in the medium subunit like that found in Escherichia coli periplasmic aldehyde oxidoreductase (EP-AOR). A funnel leading to the si-face of the isoalloxazine ring of FAD, which is narrower than those in mouse liver AOX3 and human AOX1, is also present and it is even narrower than that in EP-AOR. The environment surrounding the ring in Mb-AOX and EP-AOR is subtly different, which might account for their different abilities to use O2. A remarkable characteristic of the Mo catalytic centre in Mb-AOX is a tryptophan situated near the centre instead of the alanine present in other xanthine oxidase family members. The tryptophan residue together with other residue differences might play an important role in binding to aldehydes such as n-heptylaldehyde in Mb-AOX.
来源于细菌的杂三聚体醛氧化酶利用 O2 来催化各种醛的氧化，但不能催化芳香族 N-杂环化合物的氧化，属于黄嘌呤氧化酶家族。在本研究中，测定了来自甲基杆菌 KY4400（Mb-AOX）的重组醛氧化酶的晶体结构，分辨率为 2.5 Å。其亚基的结构类似于其他结构特征酶的相应亚基或结构域，并且在中亚基中包含一个[4Fe-4S]簇，类似于大肠杆菌周质醛氧化还原酶（EP-AOR）中的簇。一个通向 FAD 的异咯嗪环 si-面的漏斗也存在，其比鼠肝 AOX3 和人 AOX1 中的漏斗更窄。Mb-AOX 和 EP-AOR 中环周围的环境略有不同，这可能解释了它们对 O2 使用能力的不同。Mb-AOX 中 Mo 催化中心的一个显著特征是一个位于中心附近的色氨酸，而不是其他黄嘌呤氧化酶家族成员中的丙氨酸。色氨酸残基和其他残基差异可能在与 Mb-AOX 中的正庚醛等醛结合中发挥重要作用。
