Takei Mami, Kogure Syota, Yokoyama Chiaki, Kouzuma Yoshiaki, Suzuki Yoshihito
a Department of Food and Life Sciences , Ibaraki University , Inashiki , Japan.
b United Graduate School of Agricultural Science , Tokyo University of Agriculture and Technology , Fuchu-shi , Japan.
Biosci Biotechnol Biochem. 2019 Jan;83(1):129-136. doi: 10.1080/09168451.2018.1525275. Epub 2018 Oct 5.
Auxin is thought to be an important factor in the induction of galls by galling insects. We have previously shown that both galling and nongalling insects synthesize indole-3-acetic acid (IAA) from tryptophan (Trp) via two intermediates, indole-3-acetaldoxime (IAOx) and indole-3-acetaldehyde (IAAld). In this study, we isolated an enzyme that catalyzes the last step "IAAld → IAA" from a silk-gland extract of Bombyx mori. The enzyme, designated "BmIAO1", contains two 2Fe-2S iron-sulfur-cluster-binding domains, an FAD-binding domain, and a molybdopterin-binding domain, which are conserved in aldehyde oxidases. BmIAO1 causes the nonenzymatic conversion of Trp to IAAld and the enzymatic conversion of IAOx to IAA, suggesting that BmIAO1 alone is responsible for IAA production in B. mori. However, a detailed comparison of pure BmIAO1 and the crude silk-gland extract suggested the presence of other enzymes involved in IAA production from Trp. Abbreviations: BA: benzoic acid; CE: collision energy; CXP: collision cell exit potential; DP: declustering potential; IAA: indole-3-acetic acid; IBI1: IAA biosynthetic inhibitor-1; IAAld: indole-3-acetaldehyde; ICA: indole-3-carboxylic acid; IAOx: indole-3-acetaldoxime; IEtOH: indole-3-ethanol; LC-MS/MS: liquid chromatography-tandem mass spectrometry; Trp: tryptophan.
生长素被认为是瘿蚊诱导形成虫瘿的一个重要因素。我们之前已经表明，瘿蚊和非瘿蚊昆虫都能从色氨酸（Trp）经由吲哚 - 3 - 乙醛肟（IAOx）和吲哚 - 3 - 乙醛（IAAld）这两个中间体合成吲哚 - 3 - 乙酸（IAA）。在本研究中，我们从家蚕的丝腺提取物中分离出一种催化最后一步反应“IAAld→IAA”的酶。该酶被命名为“BmIAO1”，含有两个2Fe - 2S铁硫簇结合结构域、一个FAD结合结构域和一个钼蝶呤结合结构域，这些结构域在醛氧化酶中是保守的。BmIAO1能使Trp非酶促转化为IAAld，并使IAOx酶促转化为IAA，这表明仅BmIAO1就负责家蚕中IAA的产生。然而，对纯BmIAO1和粗丝腺提取物的详细比较表明，存在其他参与从Trp产生IAA的酶。缩写：BA：苯甲酸；CE：碰撞能量；CXP：碰撞池出口电位；DP：去簇电位；IAA：吲哚 - 3 - 乙酸；IBI1：IAA生物合成抑制剂 - 1；IAAld：吲哚 - 3 - 乙醛；ICA：吲哚 - 3 - 羧酸；IAOx：吲哚 - 3 - 乙醛肟；IEtOH：吲哚 - 3 - 乙醇；LC - MS/MS：液相色谱 - 串联质谱；Trp：色氨酸。
