Resumen

NETO, Brenno A. D. et al. Synthesis and enzymatic evaluation of the guanosine analogue 2-amino-6-mercapto-7-methylpurine ribonucleoside (MESG): insights into the phosphorolysis reaction mechanism based on the blueprint transition state: S_N1 or S_N2?. J. Braz. Chem. Soc. [online]. 2010, vol.21, n.1, pp. 151-156. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532010000100022.

A modified experimental procedure for the synthesis of MESG (2-amino-6-mercapto-7-methylpurine ribonucleoside) 1 has been successfully performed and its full characterization is presented. High resolution ESI(+)-MSMS indicates both the nucleoside bond cleavage as the main fragmentation in the gas phase and a possible S_N1 mechanism. Ab initio transition state calculations based on the blue print transition state support this mechanistic rationale and discard an alternative S_N2 mechanism. Assays using purine nucleoside phosphorylase (PNP) enzyme (human and M. tuberculosis sources) indicate its efficiency in the phosphorolysis of MESG and allow the quantitative determination of inorganic phosphate in real time assay.

Palabras llave : MESG; PNP enzyme; ESI; tuberculosis.