%0 Journal Article
%T The conserved Lysine69 residue plays a catalytic role in Mycobacterium tuberculosis shikimate dehydrogenase
%A Valn¨ºs S Rodrigues
%A Ardala Breda
%A Di¨®genes S Santos
%A Luiz A Basso
%J BMC Research Notes
%D 2009
%I BioMed Central
%R 10.1186/1756-0500-2-227
%X We 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 ¦ÌM; wild-type = 29 ¦ÌM) and NADPH (K69A = 30 ¦ÌM; wild-type = 11 ¦ÌM). The equilibrium dissociation constants for wild-type and K69A mutant enzymes are 32 (¡À 4) ¦ÌM and 134 (¡À 21), respectively.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.Tuberculosis (TB) remains a major global health concern. It has been estimated that one-third of the world population is infected with Mycobacterium tuberculosis, the causative agent of TB, and that 30 million people died from this disease in the last decade [1]. The epidemic of the human immunodeficiency virus, the increase in the homeless population, and the decline in health care structures and national surveillance are contributing factors to TB resurgence. Inappropriate treatment regimens and patient noncompliance in completing the therapies are associated with the emergence of multi-drug resistant TB (MDR-TB), defined as strains of M. tuberculosis resistant to at least isoniazid and rifampicin, two pivotal drugs used in the standard treatment of TB [2]. It has been reported the emergence of extensively drug-resistant (XDR) TB cases, defined as cases in persons with TB whose isolates are MDR as well as resista
%U http://www.biomedcentral.com/1756-0500/2/227