Designing of tetrazole conjoined organosilane and organosilatrane via “click approach” using Zn(II) as catalyst: Potent Mycobacterium InhA inhibitor and optical recognition of Fe(III) and Cu(II) ions

Among azoles, tetrazoles are a class of heterocycles that have salient applications in almost every field of science. Organosilicon chemistry is pondering amalgamate of different moieties and has vast applications....

Efficacy and Improved Resistance Potential of a Cofactor-Independent InhA Inhibitor of Mycobacterium tuberculosis in the C3HeB/FeJ Mouse Model

ABSTRACT AN12855 is a direct, cofactor-independent inhibitor of InhA in Mycobacterium tuberculosis. In the C3HeB/FeJ mouse model with caseous necrotic lung lesions, AN12855 proved efficacious with a significantly lower resistance frequency than isoniazid. AN12855 drug levels were better retained in necrotic lesions and caseum where the majority of hard to treat, extracellular bacilli reside. Owing to these combined attributes, AN12855 represents a promising alternative to the frontline antituberculosis agent isoniazid.

Isoniazid Activation Defects in Recombinant Mycobacterium tuberculosis Catalase-Peroxidase (KatG) Mutants Evident in InhA Inhibitor Production

ABSTRACT Mycobacterium tuberculosis KatG catalyzes the activation of the antitubercular agent isoniazid to yield an inhibitor targeting enoyl reductase (InhA). However, no firm biochemical link between many KatG variants and isoniazid resistance has been established. In the present study, six distinct KatG variants identified in clinical Mycobacterium tuberculosis isolates resistant to isoniazid were generated by site-directed mutagenesis, and the recombinant mutant proteins (KatGA110V, KatGA139P, KatGS315N, KatGL619P, KatGL634F, and KatGD735A) were purified and characterized with respect to their catalase-peroxidase activities (in terms of k cat/Km ), rates of free-radical formation from isoniazid oxidation, and, moreover, abilities to activate isoniazid. The A110V amino acid replacement did not result in significant alteration of KatG activities except that the peroxidase activity was enhanced. The other mutations, however, resulted in modestly reduced catalase and peroxidase catalytic efficiencies and, for the four mutants tested, significantly lower activities to oxidize isoniazid. Compared to the wild-type enzyme, the ability of the KatGL634F, KatGA139P, and KatGD735A variants to activate isoniazid decreased by 36%, 76%, and 73%, respectively, whereas the KatGS315N and KatGL619P variants completely lost their abilities to convert isoniazid into the InhA inhibitor. In addition, the inclusion of exogenous Mn2+ to the isoniazid activation reaction mix significantly improved the ability of wild-type and KatG mutants to produce the InhA inhibitor.