Mycobacterium tuberculosis 5′-deoxyadenosine/5′-methylthioadenosine nucleosidase (Rv0091) catalyzes the N-riboside hydrolysis of its substrates 5′-methylthioadenosine (MTA) and 5′-deoxyadenosine (5′-dAdo). 5′-dAdo is the preferred substrate, a product of radical S-adenosylmethionine-dependent enzyme reactions. Rv0091 is characterized by a ribocation-like transition state, with low N-ribosidic bond order, an N7-protonated adenine leaving group, and an activated but weakly bonded water nucleophile. DADMe-Immucillins incorporating 5′-substituents of the substrates 5′-dAdo and MTA were synthesized and characterized as inhibitors of Rv0091. 5′-Deoxy-DADMe-Immucillin-A was the most potent among the 5′-dAdo transition state analogues with a dissociation constant of 640 pM. Among the 5′-thio substituents, hexylthio-DADMe-Immucillin-A was the best inhibitor at 87 pM. The specificity of Rv0091 for the Immucillin transition state analogues differs from those of other bacterial homologues because of an altered hydrophobic tunnel accepting the 5′-substituents. Inhibitors of Rv0091 had weak cell growth effects on M. tuberculosis or Mycobacterium smegmatis but were lethal toward Helicobacter pylori, where the 5′-methylthioadenosine nucleosidase is essential in menaquinone biosynthesis. We propose that Rv0091 plays a role in 5′-deoxyadenosine recycling but is not essential for growth in these Mycobacteria.

中文翻译：

---

结核分枝杆菌5'-脱氧腺苷/ 5'-甲基硫代腺苷核酸酶的过渡态类似物抑制剂

结核分枝杆菌5'-脱氧腺苷/ 5'-甲基硫代腺苷核苷酶（Rv0091）催化其底物5'-甲基硫代腺苷（MTA）和5'-脱氧腺苷（5'-dAdo）的N-核糖水解。5'-dAdo是优选的底物，是自由基S的产物-腺苷甲硫氨酸依赖性酶反应。Rv0091的特征是具有核糖核酸样的过渡态，具有低N-核糖键序，N7质子化的腺嘌呤离去基团和活化但键合弱的水亲核试剂。合成了结合有底物5'-dAdo和MTA的5'-取代基的DADMe-伊莫西林，并将其表征为Rv0091的抑制剂。5'-Deoxy-DADMe-Immucillin-A是5'-dAdo过渡态类似物中最有效的，解离常数为640 pM。在5'-硫基取代基中，己基硫基-DADMe-伊莫西林-A在87 pM时是最好的抑制剂。Rv0091对Immucillin过渡态类似物的特异性与其他细菌同系物的特异性不同，这是因为接受5'取代基的疏水通道发生了变化。Rv0091的抑制剂对结核分枝杆菌或耻垢分枝杆菌，但对幽门螺杆菌具有致命性，其中5'-甲硫基腺苷核苷酶在甲萘醌生物合成中必不可少。我们建议Rv0091在5'-脱氧腺苷的回收中起一定作用，但对于这些分枝杆菌的生长不是必需的。