Access channel residues Ser315 and Asp137 in Mycobacterium tuberculosis catalase-peroxidase (KatG) control peroxidatic activation of the pro-drug isoniazid.

Peroxidatic activation of the anti-tuberculosis pro-drug isoniazid by Mycobacterium tuberculosis catalase-peroxidase (KatG) is regulated by gating residues of a heme access channel. The steric restriction at the bottleneck of this channel is alleviated by replacement of residue Asp137 with Ser, according to crystallographic and kinetic studies.