Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anopheles mosquitoes frequently respond to invading malaria parasites with a rejection mechanism consisting of phenoloxidase-mediated melanization of ookinetes in the mosquito midgut epithelium. The relative roles of hemolymph vs. midgut phenoloxidase in this rejection mechanism is unclear. We have separated and identified phenoloxidase isozymes from midgut and hemolymph of Anopheles stephensi by native gel electrophoresis followed by zymography. The isozymes from the 2 sites had distinctively different electrophoretic characteristics. Hemolymph possessed 2 phenoloxidase-positive bands, both of which were bifunctional molecules that oxidized monophenol as well as o-diphenol substrates. Midgut extract possessed 3 bands that migrated more rapidly than those of the hemolymph. None of these midgut bands had detectable monophenoloxidase activity; they possessed, however, a broad spectrum of diphenoloxidase activity in their ability to oxidize both o- and p-diphenol substrates, as well as the laccase substrate syringaldazine. The 2 most rapidly migrating midgut PO bands could be distinguished from the more slowly migrating band through their insensitivity to inhibition by the chelating agent tropolone. A question to be resolved in the future relates to the relative roles of hemolymph vs. midgut phenoloxidase in mosquito defense against invasive parasites.
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PMID:Electrophoretic separation and identification of phenoloxidases in hemolymph and midgut of adult Anopheles stephensi mosquitoes. 926 12

Laccase (EC 1.10.3.2) is an enzyme with p-diphenol oxidase activity that is a member of a group of proteins collectively known as multicopper, or blue copper, oxidases. Laccase is hypothesized to play an important role in insect cuticle sclerotization by oxidizing catechols in the cuticle to their corresponding quinones, which then catalyze protein cross-linking reactions. To facilitate studies of the structure, function and regulation of insect laccases, we have cloned two cDNAs for laccases from the tobacco hornworm, Manduca sexta (MsLac1 and 2), and one from the malaria mosquito, Anopheles gambiae (AgLac1). The MsLac1 and 2 cDNAs encode proteins of 801 amino acids (aa) and 760 aa, respectively, while the AgLac1 cDNA encodes a protein of 1009 aa. All three cDNAs contain putative secretion signal sequences, and the 10 histidines and one cysteine that form the copper-binding centers, as well as a methionine in the T1 copper center. Novel to the insect laccases, relative to both fungal and plant laccases, is a longer amino-terminal sequence characterized by a unique domain consisting of several conserved cysteine, aromatic, and charged residues. Northern blot analyses identified single transcripts of approximately 3.6, 3.5, and 4.4 kb for MsLac1, MsLac2, and AgLac1, respectively, and also showed that AgLac1 was expressed in all life stages of the mosquito. RT-PCR revealed that the MsLac1 transcript was most abundant in the midgut, Malpighian tubules, and epidermis, whereas the MsLac2 transcript was most abundant in the epidermis. MsLac2 showed strong expression in the pharate pupal and reduced expression in the early pupal epidermis, consistent with the laccases' presumed role in cuticle sclerotization.
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PMID:Characterization of cDNAs encoding putative laccase-like multicopper oxidases and developmental expression in the tobacco hornworm, Manduca sexta, and the malaria mosquito, Anopheles gambiae. 1472 95