title: Chorion peroxidase-mediated NADH/O(2) oxidoreduction cooperated by chorion malate dehydrogenase-catalyzed NADH production: a feasible pathway leading to H(2)O(2) formation during chorion hardening in Aedes aegypti mosquitoes.
abstract: A specific chorion peroxidase is present in Aedes aegypti and this enzyme is responsible for catalyzing chorion protein cross-linking through dityrosine formation during chorion hardening. Peroxidase-mediated dityrosine cross-linking requires H(2)O(2), and this study discusses the possible involvement of the chorion peroxidase in H(2)O(2) formation by mediating NADH/O(2) oxidoreduction during chorion hardening in A. aegypti eggs. Our data show that mosquito chorion peroxidase is able to catalyze pH-dependent NADH oxidation, which is enhanced in the presence of Mn(2+). Molecular oxygen is the electron acceptor during peroxidase-catalyzed NADH oxidation, and reduction of O(2) leads to the production of H(2)O(2), demonstrated by the formation of dityrosine in a NADH/peroxidase reaction mixture following addition of tyrosine. An oxidoreductase capable of catalyzing malate/NAD(+) oxidoreduction is also present in the egg chorion of A. aegypti. The cooperative roles of chorion malate/NAD(+)oxidoreductase and chorion peroxidase on generating H(2)O(2) with NAD(+) and malate as initial substrates were demonstrated by the production of dityrosine after addition of tyrosine to a reaction mixture containing NAD(+) and malate in the presence of both malate dehydrogenase fractions and purified chorion peroxidase. Data suggest that chorion peroxidase-mediated NADH/O(2) oxidoreduction may contribute to the formation of the H(2)O(2) required for chorion protein cross-linking mediated by the same peroxidase, and that the chorion associated malate dehydrogenase may be responsible for the supply of NADH for the H(2)O(2) production.
authors.affiliation: Department of Pathobiology, University of Illinois at Champaign-Urbana, 2001 S. Lincoln Avenue, Urbana, IL 61802, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Han
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Li
mesh_terms: D000330:Aedes / Q000502:physiology*; D000818:Animals; D002823:Chorion / Q000502:physiology*; D004527:Egg Proteins / Q000378:metabolism*; D005260:Female; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008956:Models, Chemical; D009243:NAD / Q000378:metabolism; D010053:Ovary / Q000502:physiology; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004527:Egg Proteins; C015753:chorion proteins; D009243:NAD; D006861:Hydrogen Peroxide; D008291:Malate Dehydrogenase; D009195:Peroxidase