The conserved Lysine69 residue plays a catalytic role in Mycobacterium tuberculosis shikimate dehydrogenase

The shikimate pathway is an attractive target for the development of antitubercular agents because it is essential in Mycobacterium tuberculosis, the causative agent of tuberculosis, but absent in humans. M.

tuberculosis aroE-encoded shikimate dehydrogenase catalyzes the NADPH-dependent reduction of 3-dehydroshikimate (DHS) to shikimate (SHK) in this pathway. Structural and functional studies indicate that Lysine69 may be involved in catalysis and/or substrate binding in M.

tuberculosis shikimate dehydrogenase. Investigation of the kinetic properties of mutant enzymes can bring important insights about the role of amino acid residues for M.

tuberculosis shikimate dehydrogenase.FindingsWe have performed site-directed mutagenesis, steady-state kinetics, equilibrium binding measurements and molecular modeling for both the wild-type M. tuberculosis shikimate dehydrogenase and the K69A mutant enzymes.

The apparent steady-state kinetic parameters for the M. tuberculosis shikimate dehydrogenase were determined; the catalytic constant value for the wild-type enzyme (50 s-1) is 68-fold larger than that for the mutant K69A (0.73 s-1).

There was a modest increase in the Michaelis-Menten constant for DHS (K69A=76 muM; wild-type=29 muM) and NADPH (K69A=30 muM; wild-type =11 muM). The equilibrium dissociation constants for wild-type and K69A mutant enzymes are 32 (+/- 4) uM and 134 (+/- 21), respectively.

Conclusions: Our results show that the residue Lysine69 plays a catalytic role and is not involved in substrate binding for the M.

tuberculosis shikimate dehydrogenase. These efforts on M.

tuberculosis shikimate dehydrogenase catalytic mechanism determination should help the rational design of specific inhibitors, aiming at the development of antitubercular drugs.

Author: Valnes Rodrigues-JuniorArdala BredaDiogenes SantosLuiz Basso
Credits/Source: BMC Research Notes 2009, 2:227

Published on: 2009-11-16

Copyright by the authors listed above - made available via BioMedCentral (Open Access). Please make sure to read our disclaimer prior to contacting 7thSpace Interactive. To contact our editors, visit our online helpdesk. If you wish submit your own press release, click here.

Comments Page 0 of 0

There are currently 0 comments to display.

+ Add New Comment

Custom Search