Dipteran insects -- which are responsible for the spreading of malaria, yellow fever, dengue fever, encephalitis and sleeping sickness -- like other insects are protected from their environmental enemies by their tough cuticle. At each molting cycle, the old cuticle is shed and a new cuticle is made to allow growth and development of the insect. Freshly made cuticle is soft and pale, but soon it becomes stiffened by sclerotization reactions involving adduct formation between cuticular proteins, phenols and chitin. The long term objectives is to unravel the structure and mechanism of formation of crosslinks responsible for the stabilization of cuticle and to understand the role of phenoloxidase and related enzymes in sclerotization, wound healing and melanization.
The specific aims are: a) to study the biochemistry of quinone methide sclerotization, b) to determine the structure of crosslinks formed in cuticle and c) to study the biochemistry of phenoloxidase-protease cascade in dipterans. To achieve these goals the following studies will be carried out: Studies on quinone methide sclerotization, which was discovered in this laboratory, will be continued using specifically labelled catechols and cuticular enzymes from Sarcophaga bullata and Aedes aegypti. The properties of quinone methide generating enzymes will be studied. Inhibition spectrum by a variety of quinones and catechols will be analyzed for vector control measures. The general occurrence of quinone methide sclerotization in insects will be tested. The structure of adducts formed during quinone tanning and quinone methide tanning will be determined by a combination of chemical, biochemical, and spectroscopic techniques. To assist characterization of natural isolates, synthetic adducts will be made and characterized. Quinone to beta-sclerotization ratio in destabilized mosquito cuticle will be determined. Model sclerotization studies will be continued and noninvasible probes of cuticular structure by ESR will be carried out. These studies on prophenoloxidase-protease- protease inhibitor cascade in S. bullata will be continued and extended to A. aegypti. Using appropriate antibodies, the relationship between soluble hemolymph prophenoloxidase and the cuticular phenoloxidase and the site of synthesis and localization of these components will be determined.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Tropical Medicine and Parasitology Study Section (TMP)
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University of Massachusetts Boston
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Sugumaran, Manickam (2002) Comparative biochemistry of eumelanogenesis and the protective roles of phenoloxidase and melanin in insects. Pigment Cell Res 15:2-9
Chase, M R; Sugumaran, M (2001) Genomic and cDNA sequence of prophenoloxidases from Drosophila melanogaster. Adv Exp Med Biol 484:349-62
Sugumaran, M (2001) Control mechanisms of the prophenoloxidase cascade. Adv Exp Med Biol 484:289-98
Chase, M R; Raina, K; Bruno, J et al. (2000) Purification, characterization and molecular cloning of prophenoloxidases from Sarcophaga bullata. Insect Biochem Mol Biol 30:953-67
Sugumaran, M; Nellaiappan, K; Valivittan, K (2000) A new mechanism for the control of phenoloxidase activity: inhibition and complex formation with quinone isomerase. Arch Biochem Biophys 379:252-60
Sugumaran, M; Nellaiappan, K; Amaratunga, C et al. (2000) Insect melanogenesis. III. Metabolon formation in the melanogenic pathway-regulation of phenoloxidase activityy by endogenous dopachrome isomerase (decarboxylating) from Manduca sexta. Arch Biochem Biophys 378:393-403
Sugumaran, M (2000) Oxidation chemistry of 1,2-dehydro-N-acetyldopamines: direct evidence for the formation of 1,2-dehydro-N-acetyldopamine quinone. Arch Biochem Biophys 378:404-10
Sugumaran, M; Nellaiappan, K (2000) Characterization of a new phenoloxidase inhibitor from the cuticle of Manduca sexta. Biochem Biophys Res Commun 268:379-83
Sugumaran, M; Duggaraju, R; Generozova, F et al. (1999) Insect melanogenesis. II. Inability of Manduca phenoloxidase to act on 5,6-dihydroxyindole-2-carboxylic acid. Pigment Cell Res 12:118-25
Sugumaran, M; Duggaraju, P; Jayachandran, E et al. (1999) Formation of a new quinone methide intermediate during the oxidative transformation of 3,4-dihydroxyphenylacetic acids: implication for eumelanin biosynthesis. Arch Biochem Biophys 371:98-106

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