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Insect Biochem Mol Biol. 2003 Feb;33(2):163-71.

Cloning and characterization of trypsin- and chymotrypsin-like proteases from the midgut of the sand fly vector Phlebotomus papatasi.

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  • 1Intracellular Parasite Biology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, 4 Center Drive, Building 4, Room 126, MSC-0425, NIH, Bethesda, MD 20892-0425, USA.


Trypsin and chymotrypsin serine proteases are the main digestive proteases in Diptera midguts and are also involved in many aspects of the vector-parasite relationship. In sand flies, these proteases have been shown to be a potential barrier to Leishmania growth and development within the midgut. Here we describe the sequence and partial characterization of six Phlebotomus papatasi midgut serine proteases: two chymotrypsin-like (Ppchym1 and Ppchym2) and four trypsin-like (Pptryp1-Pptryp4). All six enzymes show structural features typical to each type, including the histidine, aspartic acid, and serine (H/D/S) catalytic triad, six conserved cysteine residues, and other amino acid residues involved in substrate specificity. They also show a high degree of homology (40-60% identical residues) with their counterparts from other insect vectors, such as Anopheles gambiae and Aedes aegypti. The mRNA expression profiles of these six proteases vary considerably: two trypsin-like proteases (Pptryp1 and Pptryp2) are downregulated and one (Pptryp4) upregulated upon blood feeding. The two chymotrypsin-like enzymes display expression behavior similar to that of the early and late trypsins from Ae. aegypti.

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