Phenoloxidase (PO)

Phenoloxidase is a copper-containing oxidoreductase enzyme that catalyzes the oxidation of phenolic compounds to quinones, which are then converted to melanin. This enzyme plays a central role in the biology of invertebrates, especially insects, where it is essential for the innate immune system (defense against pathogens by melanization), sclerotization and pigment formation of the cuticle, and wound healing. Phenoloxidase is synthesized as an inactive precursor (prophenoloxidase), which is activated in response to infection or injury. The enzyme's activity leads to the production of melanin and other cytotoxic intermediates that encase pathogens or seal wounds. Inhibition of phenoloxidase activity can impair immune defense and developmental processes in arthropods. While phenoloxidase is not a major therapeutic target in humans, it is a significant target in insecticide development and pest control strategies and has been studied as a model system for understanding immune and repair processes in invertebrates. In plant and fungal systems, the term "phenoloxidase" often includes related multicopper oxidase enzymes such as laccases and peroxidases, though in animals, especially insects, it typically refers specifically to prophenoloxidase/phenoloxidase.

Other names

monophenol monooxygenasetyrosinase (in context)prophenoloxidase (inactive zymogen form)multicopper oxidase (family)

Enzymatic catalysis of phenolic compound oxidation to quinones, leading to melanin formation and sclerotization