Kinetic characterization of inosine monophosphate dehydrogenase of Leishmania donovani
Kinetic characterization of inosine monophosphate dehydrogenase of Leishmania donovani
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DOI：
10.1016/j.molbiopara.2006.11.007
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发表时间：
2007-03-01
影响因子：
1.5
通讯作者：
Jardim, Armando
中科院分区：
文献类型：
--
作者：
Dobie, Fredrick;Berg, Amanda;Jardim, Armando
锥虫属原生动物病原体是嘌呤营养缺陷型，其高度依赖于酶mosine单磷酸脱氢酶（IMPDH）来合成鸟苷酸核苷酸。在E.大肠杆菌的酶活测定表明，该酶对底物IMP和NAD（+）具有高度特异性，Km（app）值分别为33和390 μ M。与其它IMPDH相反，LdIMPDH在高浓度NAD（+）下不表现出底物抑制。动力学研究表明，XMP和GMP的抑制剂，K-i值类似的26和2 - 10 μ M，分别表明，这些核苷酸可以调节LdIMPDH活性。霉酚酸也是一种有效的L. donovani IMPDH，Ki值类似于25 nM。共聚焦免疫荧光显微镜和亚细胞分级定位LdIMPDH的糖体。蛋白质-蛋白质相互作用分析表明，LdIMPDH与糖体蛋白分选受体LdPEX 5紧密相关。(c)2006 Elsevier B. V.保留所有权利。
Trypanosomatid protozoan pathogens are purine auxotrophs that are highly dependent on the enzyme mosine monophosphate dehydrogenase (IMPDH) for the synthesis of guanylate nucleotides. Enzymatic characterization of the Leishmania donovani IMPDH (LdIMPDH) overexpressed in E. coli revealed that this enzyme was highly specific for the substrates IMP and NAD(+) with K-m(app) values of 33 and 390 mu M, respectively. In contrast to other IMPDHs, LdIMPDH exhibits no substrate inhibition in high concentrations of NAD(+). Kinetic studies revealed that, XMP and GMP were inhibitors with K-i values of similar to 26 and 2 10 mu M, respectively, suggesting that these nucleotides may regulate LdIMPDH activity. Mycophenolic acid was also a potent inhibitor of L. donovani IMPDH with a Ki value of similar to 25 nM. Confocal immunofluorescence microscopy and subcellular fractionation localized LdIMPDH to the glycosome. Protein-protein interaction assays revealed that LdIMPDH associated tightly with glycosomal protein sorting receptor LdPEX5. (c) 2006 Elsevier B.V. All rights reserved.