Biochemistry of the initial steps of mycothiol biosynthesis
Biochemistry of the initial steps of mycothiol biosynthesis
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DOI：
10.1074/jbc.m604724200
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发表时间：
2006-11-10
影响因子：
4.8
通讯作者：
Fahey, Robert C.
中科院分区：
文献类型：
--
作者：
Newton, Gerald L.;Ta, Philong;Fahey, Robert C.
分枝杆菌硫醇是分枝杆菌产生的主要硫醇，是结核分枝杆菌生长所必需的。真菌硫醇生物合成的最后三个步骤已经完全阐明，但最初的步骤还不清楚。糖基转移酶MshA是产生真菌硫醇前体1-O-（2-乙酰氨基-2-脱氧-α-D-吡喃葡萄糖基）-D-肌醇所必需的，但其底物和直接产物未知。在这项研究中，我们表明，N-乙酰葡糖胺供体是UDP-N-乙酰葡糖胺和N-乙酰葡糖胺受体是1 L-肌醇1-磷酸。反应生成UDP和1-O-（2-乙酰氨基-2-脱氧-α-D-吡喃葡萄糖基）-D-肌-肌醇3-磷酸。利用M.对于smeg-1 mc（2）155，用肌醇、1D-肌醇1-磷酸或肌醇2-磷酸作为N-乙酰葡糖胺受体几乎没有活性。磷酸酶，命名为MshA 2，需要将1-O-（2-乙酰氨基-2-脱氧-D-吡喃葡萄糖基）-D-肌醇3-磷酸去磷酸化以产生1-O-（2-乙酰氨基-2-脱氧-α-D-吡喃葡萄糖基）-D-肌醇。后者被脱乙酰化，与半胱氨酸连接，半胱氨酰氨基被乙酰辅酶A乙酰化，以完成真菌硫醇生物合成途径。在耻垢分枝杆菌中，肌-[C-14]肌醇的摄取和浓缩是快速的，并导致放射性标记的肌醇1-磷酸和肌二硫醇的产生。这表明存在肌肌醇转运蛋白和产生1 L-肌肌醇1-磷酸的激酶。真菌硫醇生物合成的生化途径现已完全阐明。
Mycothiol is the major thiol produced by mycobacteria and is required for growth of Mycobacterium tuberculosis. The final three steps in the biosynthesis of mycothiol have been fully elucidated but the initial steps have been unclear. A glycosyltransferase, MshA, is required for production of the mycothiol precursor, 1-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-D-myo-inositol, but its substrates and immediate products were unknown. In this study, we show that the N-acetylglucosamine donor is UDP-N-acetylglucosamine and that the N-acetylglucosamine acceptor is 1L-myo-inositol 1-phosphate. The reaction generates UDP and 1-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-D-myo-inositol 3-phosphate. Using cell-free extracts of M. smegmatis mc(2)155, little activity was obtained with myo-inositol, 1D-myo-inositol 1-phosphate, or myo-inositol 2-phosphate as the N-acetylglucosamine acceptor. A phosphatase, designated MshA2, is required to dephosphorylate 1-O-(2-acetamido-2-deoxy-D-glucopyranosyl)-D- myo-inositol 3-phosphate to produce 1-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-D-myo- inositol. The latter is deacetylated, ligated with cysteine, and the cysteinyl amino group acetylated by acetyl-CoA to complete the mycothiol biosynthesis pathway. Uptake and concentration of myo-[C-14] inositol is rapid in Mycobacterium smegmatis and leads to production of radio labeled inositol1-phosphate and my cothiol. This demonstrates the presence of a myo- inositol transporter and a kinase that generates 1L-myo-inositol1-phosphate. The biochemical pathway of mycothiol biosynthesis is now fully elucidated.