PEROXIDASIN - A NOVEL ENZYME-MATRIX PROTEIN OF DROSOPHILA DEVELOPMENT

Peroxidasin is a novel protein combining peroxidase and extracellular matrix motifs. Hemocytes differentiate early from head mesoderm, make peroxidasin and later phagocytose apoptotic cells. As hemocytes spread throughout the embryo, they synthesize extracellular matrix and perox idasin, incorporating it into completed basement membranes. Cultured c ells secrete peroxidasin; it occurs in larvae and adults. Each 1512 re sidue chain of the three-armed, disulfide-linked homotrimer combines a peroxidase domain with six leucine-rich regions, four Ig loops, a thr ombospondin/procollagen homology and an amphipathic alpha-helix. The p eroxidase domain is homologous with human myeloperoxidase and eosinoph il peroxidase. This heme protein catalyzes H2O2-driven radioiodination s, oxidations and formation of dityrosine. We propose that peroxidasin functions uniquely in extracellular matrix consolidation, phagocytosi s and defense.