Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada.
Biochemistry. 2010 Mar 30;49(12):2672-9. doi: 10.1021/bi901432d.
MenD is a thiamin diphosphate-dependent enzyme catalyzing the first unique step in menaquinone biosynthesis in bacteria. We have synthesized acylphosphonate ester analogues of alpha-ketoglutarate, a substrate of MenD. These compounds are competitive inhibitors of MenD, with K(i) values as low as 700 nM. Observed structure-activity relationships are in notable contrast to those reported previously for succinylphosphonate inhibition of the alpha-ketoglutarate dehydrogenase complex, despite the apparent homology of these enzymes, and the identical decarboxylation reactions catalyzed. Inhibiting menaquinone biosynthesis is a proposed approach to inhibiting Mycobacterium tuberculosis growth. These inhibitors showed no significant inhibition of M. tuberculosis growth in vitro under aerobic and hypoxic conditions but give new information about the binding characteristics of the MenD active site. Site-directed mutation of Ser391 to alanine had only a minor effect on catalysis, but even the conservative mutation of Arg395 to lysine had a significant effect on the catalytic processing of isochorismate.
MenD 是一种依赖硫胺素二磷酸的酶，催化细菌中menaquinone 生物合成的第一个独特步骤。我们已经合成了 MenD 的底物α-酮戊二酸的酰基膦酸酯类似物。这些化合物是 MenD 的竞争性抑制剂，其 K(i) 值低至 700 nM。观察到的结构-活性关系与先前报道的琥珀酰膦酸抑制α-酮戊二酸脱氢酶复合物的情况形成鲜明对比，尽管这些酶具有明显的同源性，并且催化的脱羧反应相同。抑制menaquinone 生物合成是抑制结核分枝杆菌生长的一种方法。这些抑制剂在有氧和缺氧条件下对结核分枝杆菌的体外生长没有明显的抑制作用，但为 MenD 活性位点的结合特性提供了新的信息。将 Ser391 突变为丙氨酸对催化作用的影响很小，但即使将保守的 Arg395 突变为赖氨酸也对异柠檬酸的催化加工有显著影响。
