[The mechanism of action of isoniazid. A chemical model of activation].

The antituberculosis drug isoniazid (INH) is quickly oxidized by stoichiometric amounts of manganese(III)-pyrophosphate. In the presence of the nicotinamide coenzyme, the INH oxidation produced the formation of INH-NAD(H) adducts which are potential competitive inhibitors of the enoyl-acyl carrier protein reductase InhA, an INH target in the biosynthetic pathway for mycolic acids. Manganese(III)-pyrophosphate is an efficient alternative oxidant to mimick the activity of the Mycobacterium tuberculosis KatG catalase-peroxidase and will be useful for further mechanistic studies of INH activation and for structural investigations on reactive INH species and resulting InhA inhibitors.