Peroxiredoxin (PRX) family, AhpE-like subfamily; composed of proteins similar to Mycobacterium tuberculosis AhpE. AhpE is described as a 1-cys PRX because of the absence of a resolving cysteine. The structure and sequence of AhpE, however, show greater similarity to 2-cys PRXs than 1-cys PRXs. PRXs are thiol-specific antioxidant (TSA) proteins that confer a protective role in cells through their peroxidase activity in which hydrogen peroxide, peroxynitrate, and organic hydroperoxides are reduced and detoxified using reducing equivalents derived from either thioredoxin, glutathione, trypanothione and AhpF. The first step of catalysis is the nucleophilic attack by the peroxidatic cysteine on the peroxide leading to the formation of a cysteine sulfenic acid intermediate. The absence of a resolving cysteine suggests that functional AhpE is regenerated by an external reductant. The solution behavior and crystal structure of AhpE show that it forms dimers and octamers.
Comment:Deprotonation of the catalytic cysteine thiol is facilitated by H-bonding with the threonine or serine hydroxyl group, and the positive charge of the arginine sidechain.
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