Nonproteolytic serine proteinase homologs are involved in prophenoloxidase activation in the tobacco hornworm, Manduca sexta.

摘要: In insects, the prophenoloxidase activation system is a defense mechanism against parasites and pathogens. Recognition of or pathogens by pattern recognition receptors triggers serine proteinase cascade, leading to prophenoloxidase-activating (PAP). PAP converts inactive (proPO) active phenoloxidase (PO), which then catalyzes oxidation phenolic compounds that can polymerize form melanin. Because quinone intermediates melanin are toxic both hosts pathogens, proPO must be tightly regulated localized. We report here purification cDNA cloning homologs (SPHs) from tobacco hornworm, Manduca sexta, interact with PAP-1 in activation. Two SPHs were co-purified plasma M. sexta larvae immulectin-2, C-type lectin binds bacterial lipopolysaccharide. They contain an amino-terminal clip domain connected carboxyl-terminal proteinase-like domain. alone cannot efficiently activate proPO, but mixture was much more effective for Immulectin-2, hemolymph bound immobilized recombinant SPH-1, indicating complex containing these proteins may exist hemolymph. Since immulectin-2 receptor surface carbohydrates on such protein localize SPH, function as mediator recruit site infection.