Drugs Against Mycobacterium tuberculosis 3-Isopropylmalate Dehydrogenase Can be Developed Using Homologous Enzymes as Surrogate Targets
Eva Graczer, Andras Bacso, Denes Konya, Adrian Kazi, Tibor Soos, Laura Molnar, Tamas Szimler, Laszlo Beinrohr, Andras Szilagyi, Peter Zavodszky and Maria VasAffiliation:
Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H- 1117 Budapest, Magyar tudósok korutja 2., Hungary; H-1519 Budapest, P. O. Box 286., Hungary.
Abstract3-Isopropylmalate dehydrogenase (IPMDH) from Mycobacterium tuberculosis (Mtb) may be a target for specific drugs against this pathogenic bacterium. We have expressed and purified Mtb IPMDH and determined its physicalchemical and enzymological properties. Size-exclusion chromatography and dynamic light scattering measurements (DLS) suggest a tetrameric structure for Mtb IPMDH, in contrast to the dimeric structure of most IPMDHs. The kinetic properties (kcat and Km values) of Mtb IPMDH and the pH-dependence of kcat are very similar to both Escherichia coli (Ec) and Thermus thermophilus (Tt) IPMDHs. The stability of Mtb IPMDH in 8 M urea is close to that of the mesophilic counterpart, Ec IPMDH, both of them being much less stable than the thermophilic (Tt) enzyme. Two known IPMDH inhibitors, O-methyl oxalohydroxamate and 3-methylmercaptomalate, have been synthesised. Their inhibitory effects were found to be independent of the origin of IPMDHs. Thus, experiments with either Ec or Tt IPMDH would be equally relevant for designing specific inhibitory drugs against Mtb IPMDH.
Enzyme kinetics, expression, isopropylmalate dehydrogenase, inhibition, Mycobacterium tuberculosis, purification, physical-chemical characterization.
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