Transition State Structure and Inhibition of Rv0091, a 5′-Deoxyadenosine/5′-methylthioadenosine Nucleosidase from <i>Mycobacterium tuberculosis</i>
作者:Hilda A. Namanja-Magliano、Christopher F. Stratton、Vern L. Schramm
DOI:10.1021/acschembio.6b00144
日期:2016.6.17
Si-Methylthioadertosine/S-Oenosylhornocxsteine nucleoSidase (MTAN) is a bacterial enzyme that catalyzes the hydrolysis of the N-ribosidic bond- in "S'-inethylthioadenoshie (MTA) and-S-adenosylhom-ocysteitie (SAH). MTAN activity has- be,en: linked to quorum Sensing pathways, polyaMine biosynthesis, and adenine salVage Previously the aiding sequence Of Rv0091 was annotated as a putative (MTA) in Mycobacterium tuberculosis. Rv0091 was expressed 14 Escherithia coli, purified :to -homogeneity., and shown to be a homodimer, consistent with MTANs from other -microorganisms. Substrate specificity for Rv0091 gave a preference for,SCcleoxya,deriosine relative to MTA or SAH. Intrinsic :kinetic isbtope':effects (KIEs) for'.the hydrolysis of [1'-H-3], [1'-C-14] [5-H-3(2)]; and [9-(15)]MTA. were determined to be 1.207, 1.038, 0:998, 1.021, and 0.998, respectively. A model for the transition state structure of Rv0091 'was determined by matching KIE values predicted via quantum cheinical calculations to the'intrinsic KIEs. The transition state shows -a subStantial loss of Cl-,1 N9 bond order,: well -developed oxocarbenium character ofthe ribosyl ring and weak participation of the Water nueleophile. Electrostatic potential surface maps for the Ry0091 transition state structure show, siMilarity to DADMe-irrimucillin yansition state analogues. DADMe-lim-nucillirt transition state analogues showed strong inhibiticin of Rv0091, with:the most potent inhibitor (514iexylthio-DADMe4inmut'illinA): displaying a Ki value of 87 pM.