Extracellular glutathione peroxidase from the blood-sucking bug, Rhodnius prolixus

Glutathione peroxidase (GPX) activity was measured in several tissues of th e blood-sucking bug, Rhodnius prolixus. In contrast to the pattern found in vertebrates, where GPX is predominantly intracellular, the highest levels of this enzyme in Rhodnius were found in the hemolymph. The hemolymph gluta thione-dependent peroxidase accepted both H2O2 and t-butyl hydroperoxide as substrates. This fact, together with the absolute glutathione dependence, inhibition by mercapto-succinate, insensitivity to cyanide, and a molecular mass (100.7 kDa) similar to vertebrate GPXs, led us to attribute this pero xidatic activity to a Se-dependent enzyme. Hemolymph GPX specific activity increases during development and a twofold stimulation was observed after a n oxidative challenge with hemin, suggesting that enzyme synthesis is under regulatory control. A role for extracellular GPX as an antioxidant protect ion against oxidative damage produced by heme derived from digestion of blo od hemoglobin is discussed. Arch. Insect Biochem. Physiol. 41:171-177, 1999 . (C) 1999 Wiley-Liss, Inc.