Identification of two scyllo-inositol dehydrogenases in Bacillus subtilis
Identification of two scyllo-inositol dehydrogenases in Bacillus subtilis
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DOI：
10.1099/mic.0.037499-0
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发表时间：
2010-05-01
期刊：
影响因子：
2.8
通讯作者：
Yoshida, Ken-ichi
中科院分区：
文献类型：
--
作者：
Morinaga, Tetsuro;Ashida, Hitoshi;Yoshida, Ken-ichi
鲨肌醇 (SI) 是肌醇的立体异构体，其分解代谢尚未在细菌中得到表征。我们发现枯草芽孢杆菌 168 能够使用 SI 作为其唯一碳源生长，并且这种生长依赖于肌醇（MI；另一种肌醇异构体，自然界中丰富的）分解代谢的功能性 iol 操纵子。先前的研究阐明枯草芽孢杆菌中的 MI 分解代谢途径包含由一系列 lol 酶催化的多个逐步反应。该途径的第一步将 MI 转化为鲨肌糖 (SIS)，并涉及 MI 脱氢酶 lolG。由于lolG不作用于SI，我们怀疑可能存在另一种酶将SI转化为SIS，即SI脱氢酶。在整个基因组中，已经鉴定了七个与 iolG 旁系同源的基因，其中两个 iolX 和 iolW（以前分别称为 yisS 和 yvaA）被选为推定的 SI 脱氢酶的候选基因，因为当枯草芽孢杆菌在含有 SI 的培养基上生长时，它们都显着表达。 iolX 和 iolW 被克隆到埃希菲赤氏菌 (Eschefichia colt) 中，并且两者均编码功能酶，揭示了枯草芽孢杆菌 (B. subtilis) 中的两种不同的 SI 脱氢酶。由于 iolX 失活会损害以 SI 作为碳源的生长，因此 lolX 被确定为 SI 分解代谢所需的分解代谢酶，并且显示出其具有 NAD(+) 依赖性。 lolW 的生理作用尚不清楚，但它可能能够通过 NADPH 氧化从 SIS 产生 SI。
scyllo-Inositol (SI) is a stereoisomer of inositol whose catabolism has not been characterized in bacteria. We found that Bacillus subtilis 168 was able to grow using SI as its sole carbon source and that this growth was dependent on a functional iol operon for catabolism of myo-inositol (MI; another inositol isomer, which is abundant in nature). Previous studies elucidated the MI catabolic pathway in B. subtilis as comprising multiple stepwise reactions catalysed by a series of lol enzymes. The first step of the pathway converts MI to scyllo-inosose (SIS) and involves the MI dehydrogenase lolG. Since lolG does not act on SI, we suspected that there could be another enzyme converting SI into SIS, namely an SI dehydrogenase. Within the whole genome, seven genes paralogous to iolG have been identified and two of these, iolX and iolW (formerly known as yisS and yvaA, respectively), were selected as candidate genes for the putative SI dehydrogenase since they were both prominently expressed when B. subtilis was grown on medium containing SI. iolX and iolW were cloned in Eschefichia colt and both were shown to encode a functional enzyme, revealing the two distinct SI dehydrogenases in B. subtilis. Since inactivation of iolX impaired growth with SI as the carbon source, lolX was identified as a catabolic enzyme required for SI catabolism and it was shown to be NAD(+) dependent. The physiological role of lolW remains unclear, but it may be capable of producing SI from SIS with NADPH oxidation.