InterPro domain: IPR036851

Chloroperoxidase (CPO), also known as Heme haloperoxidase, is a ~250 residue heme-containing glycoprotein that is secreted by various fungi. Chloroperoxidase was first identified in Caldariomyces fumago where it catalyzes the hydrogen peroxide-dependent chlorination of cyclopentanedione during the biosynthesis of the antibiotic caldarioymcin. Additionally, heme haloperoxidase catalyzes the iodination and bromination of a wide range of substrates. Besides performing H2O2-dependent halogenation reactions, the enzyme catalyzes dehydrogenation reactions. Chloroperoxidase also functions as a catalase, facilitating the decomposition of hydrogen peroxide to oxygen and water. Furthermore, chloroperoxidase catalyzes P450-like oxygen insertion reactions. The capability of chloroperoxidase to perform these diverse reactions makes it one of the most versatile of all known heme proteins [ 1 , 2 ].

Despite functional similarities with other heme enzymes, chloroperoxidase folds into a novel tertiary structure dominated by eight helical segments [ 3 ]. Structurally, chloroperoxidase is unique, but it shares features with both peroxidases and P450 enzymes. As in cytochrome P450 enzymes, the proximal heme ligand is a cysteine, but similar to peroxidases, the distal side of the heme is polar. However, unlike other peroxidases, the normally conserved distal arginine is lacking and the catalytic acid base is a glutamic acid and not a histidine [ 4 ].

1. Heme-thiolate haloperoxidases: versatile biocatalysts with biotechnological and environmental significance. Appl. Microbiol. Biotechnol. 71, 276-88
2. Chloroperoxidase, a janus enzyme. Biochemistry 47, 2997-3003
3. The crystal structure of chloroperoxidase: a heme peroxidase--cytochrome P450 functional hybrid. Structure 3, 1367-77
4. Crystal structures of chloroperoxidase with its bound substrates and complexed with formate, acetate, and nitrate. J. Biol. Chem. 281, 23990-8