myo-inositol catabolism in Bacillus subtilis
myo-inositol catabolism in Bacillus subtilis
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DOI：
10.1074/jbc.m708043200
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发表时间：
2008-04-18
影响因子：
4.8
通讯作者：
Fujita, Yasutaro
中科院分区：
文献类型：
--
作者：
Yoshida, Ken-Ichi;Yamaguchi, Masanori;Fujita, Yasutaro
枯草芽孢杆菌的iolABCDEFGHIJ操纵子负责涉及多个和逐步反应的肌醇催化。先前的研究表明，IolG和IolE是第一和第二反应的酶，即肌醇脱氢生成2-酮基-肌醇和随后脱水生成3D-（3，5/4）-三羟基环己烷-1，2-二酮。在本研究中，第三个反应被证明是3D-（3，5/4）-三羟基环己烷-1，2-二酮的水解由Iold D生成5-脱氧-D-葡萄糖醛酸。第四个反应是5-脱氧-D-葡萄糖醛酸通过IolB异构化以产生2-脱氧-5-酮基-D-葡萄糖酸。接着，在第五反应中，2-脱氧-5-酮基-D-葡萄糖酸被IolC激酶磷酸化，得到2-脱氧-5-酮基-D-葡萄糖酸6-磷酸。IolR被认为是控制转录操纵子转录的阻遏物。在该反应中，2-脱氧-5-酮基-D-葡萄糖酸6-磷酸似乎是通过拮抗IolR的DNA结合而作为诱导剂起作用的中间体。最后，IolJ被证明是第六个反应的特异性醛缩酶，该反应将2-脱氧-5-酮-D-葡萄糖酸6-磷酸裂解成二羟丙酮磷酸和丙二酸半醛。前者是已知的糖酵解中间体，而后者先前显示通过IolA催化的反应转化为乙酰辅酶A和CO2。B中肌醇分解代谢途径的净结果。因此，枯草杆菌是将肌醇转化为磷酸二羟丙酮、乙酰辅酶A和CO2的等摩尔混合物。
The iolABCDEFGHIJ operon of Bacillus subtilis is responsible for myo-inositol catabolism involving multiple and stepwise reactions. Previous studies demonstrated that IolG and IolE are the enzymes for the first and second reactions, namely dehydrogenation of myo-inositol to give 2-keto-myo-inositol and the subsequent dehydration to 3D-(3,5/4)-trihydroxycyclohexane1,2- dione. In the present studies the third reaction was shown to be the hydrolysis of 3D-(3,5/4)-trihydroxycyclohexane-1,2-dione catalyzed by IolD to yield 5-deoxy-D-glucuronic acid. The fourth reaction was the isomerization of 5-deoxy-D-glucuronic acid by IolB to produce 2-deoxy-5-keto-D-gluconic acid. Next, in the fifth reaction 2-deoxy-5-keto-D-gluconic acid was phosphorylated by IolC kinase to yield 2-deoxy-5-keto-D-gluconic acid 6-phosphate. IolR is known as the repressor controlling transcription of the iol operon. In this reaction 2-deoxy-5-keto-D-gluconic acid 6-phosphate appeared to be the intermediate acting as inducer by antagonizing DNA binding of IolR. Finally, IolJ turned out to be the specific aldolase for the sixth reaction, the cleavage of 2-deoxy-5-keto-D-gluconic acid 6-phosphate into dihydroxyacetone phosphate and malonic semialdehyde. The former is a known glycolytic intermediate, and the latter was previously shown to be converted to acetyl-CoA and CO2 by a reaction catalyzed by IolA. The net result of the inositol catabolic pathway in B. subtilis is, thus, the conversion of myo-inositol to an equimolar mixture of dihydroxyacetone phosphate, acetyl-CoA, and CO2.