Drosophila peroxidasin is an extracellular matrix-associated peroxidase (Horikoshi et al., 1999 [PubMed 10441517]). It is expressed exclusively in hemocytes derived from head mesoderm at a very early stage of differentiation. Peroxidasin exists as a homotrimer with a unique hybrid structure that combines an enzymatically functional peroxidase domain with motifs that are typically found in extracellular matrix-associated proteins. It is a secreted protein that contains a secretory recognition sequence at its N terminus. Peroxidasin catalyzes hydrogen peroxide-driven radioiodination, oxidations, and the formation of dityrosine in vitro. It is also thought to function in extracellular matrix consolidation, phagocytosis, and defense.