Amphitrite ornata dehaloperoxidase (DHP) is a heme enzyme with a globin structure, which is capable of oxidizing para-halogenated phenols to the corresponding quinones. Cloning, high-level expression, and purification of recombinant DHP are described. Recombinant DHP was assayed by stopped-flow experiments for its ability to oxidatively debrominate 2,4,6-tribromophenol (TBP). The enzymatic activity of the ferric form of recombinant DHP is intermediate between that of a typical peroxidase (horseradish peroxidase) and a typical globin (horse heart myoglobin). The present study shows that, unlike other known peroxidases, DHP activity requires the addition of substrate, TBP, prior to the cosubstrate, peroxide. The presence of a substrate-binding site in DHP is consistent with a two-electron oxidation mechanism and an obligatory order for activation of the enzyme by addition of the substrate prior to the cosubstrate.