Hemoglobinase activity of a cysteine protease from the ixodid tick Haemaphysalis longicornis.

Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
Parasitology International (Impact Factor: 2.3). 06/2009; 58(3):232-7. DOI: 10.1016/j.parint.2009.05.003
Source: PubMed

ABSTRACT We report here the molecular characterization and possible function of a cysteine protease (termed HlCPL-A) identified in the midgut of the hard tick Haemaphysalis longicornis. HlCPL-A is a 333 amino acid protein belonging to the papain family of the cysteine protease. A construct encoding proHlCPL-A was expressed in Escherichia coli and purified as both procathepsin L and active processed cathepsin L forms. The HlCPL-A gene expression was up-regulated by blood-feeding process. HlCPL-A exhibited substrate specificity against synthetic peptidyl substrates (Z-Phe-Arg-MCA and Z-Arg-Arg-MCA; k(cat)/K(m)=0.19 and 0.0023 M(-1) S(-1), respectively). The proteolytic activity of HlCPL-A was inhibited by leupeptin, antipain and E-64 but was unaffected by pepstatin. HlCPL-A was capable of degrading bovine hemoglobin at pH 3.2 to 5.6. These results suggest that HlCPL-A may play important roles in the digestion of host hemoglobin in ticks.

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