The salivary catechol oxidase/peroxidase activities of the mosquito Anopheles albimanus

Salivary gland homogenates from adult female Anopheles albimanus mosquitoes relaxed aortic rings preconstricted with noradrenaline (NA). This relaxation is slow and is due to destruction of NA. Incubation of NA with the homogenate yielded a product with a spectrum consistent with the corresponding adrenochrome. Oxidation of NA was enhanced by a superoxide generation system and inhibited by the combined action of superoxide dismutase and catalase. Additionally, peroxidase activity on both synthetic (o-dianisidine) and biologically active (serotonin) substrates was also present in the salivary gland homogenates, this latter activity requiring hydrogen peroxide. Noradrenaline oxidation, serotonin and o-dianisidine peroxidation and vasodilation all co-elute with a heme protein of relative molecular mass 50,000, as determined by molecular sieving chromatography. Peroxidase activity was localized in the posterior (female-specific) lobes of salivary glands and was also detected in nitrocellulose membranes probed by hungry mosquitoes. Protein and peroxidase activities were significantly lower in salivary glands of mosquitoes after probing and feeding on blood. It is suggested that adult female Anopheles albimanus mosquitoes contain a salivary heme peroxidase that functions during blood finding and blood feeding by destroying hemostatically active biogenic amines released by the vertebrate host during tissue destruction.