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Molecular characterization of a blood‐induced serine carboxypeptidase from the ixodid tick Haemaphysalis longicornis
Author(s) -
Motobu Maki,
Tsuji Naotoshi,
Miyoshi Takeharu,
Huang Xiaohong,
Islam M. K.,
Alim M. A.,
Fujisaki Kozo
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05852.x
Subject(s) - haemaphysalis longicornis , midgut , biology , biochemistry , blood meal , carboxypeptidase , serine , serine protease , vacuole , amino acid , enzyme , microbiology and biotechnology , tick , protease , ixodidae , zoology , botany , cytoplasm , virology , larva
Ticks feed exclusively on blood to obtain their nutrients, but the gene products that mediate digestion processes in ticks remain unknown. We report the molecular characterization and possible function of a serine carboxypeptidase (HlSCP1) identified in the midgut of the hard tick Haemaphysalis longicornis . HlSCP1 consists of 473 amino acids with a peptidase S10 family domain and shows structural similarity with serine carboxypeptidases reported from other arthropods, yeasts, plants and mammals. Endogenous HlSCP1 is strongly expressed in the midgut and is supposed to localize at lysosomal vacuoles and on the surface of epithelial cells. Endogenous HlSCP1, identified as a 53 kDa protein with p I value of 7.5, was detected in the membrane/organelle fraction isolated from the midgut, and its expression was upregulated during the course of blood‐feeding. Enzymatic functional assays revealed that a recombinant HlSCP1 (rHlSCP1) expressed in yeast efficiently hydrolyzed the synthetic substrates specific for cathepsin A and thiol protease over a broad range of pH and temperature values. Furthermore, rHlSCP1 was shown to cleave hemoglobin, a major component of the blood‐meal. Our results suggest that HlSCP1 may play a vital role in the digestion of the host's blood‐meal.