Molecular and biochemical characterization of hemoglobinase, a cysteine proteinase, in Paragonimus westermani

Abstract

Abstract:The mammalian trematode Paragonimus westermani is a typical digenetic parasite, which can cause paragonimiasis in humans. Host tissues and blood cells are important sources of nutrients for development, growth and reproduction of P. westermani. In this study, a cDNA clone encoding a 47 kDa hemoglobinase of P. westermani was characterized by sequencing analysis, and its localization was investigated immunohistochemically. The phylogenetic tree prepared based on the hemoglobinase gene showed high homology with hemoglobinases of Fasciola hepatica and Schistosoma spp. Moreover, recombinant P. westermani hemoglobinase degradaded human hemoglobin at acidic pH (from 3.0 to 5.5) and its activity was almost completely inhibited by E-64, a cysteine proteinase inhibitor. Immunohistochemical studies showed that P. westermani hemoglobinase was localized in the epithelium of the adult worm intestine implying that the protein has a specific function. These observations suggest that hemoglobinase may act as a digestive enzyme for acquisition of nutrients from host hemoglobin. Further investigations may provide insights into hemoglobin catabolism in P. westermani.

Asparaginyl endopeptidase from the carcinogenic liver fluke, Opisthorchis viverrini, and its potential for serodiagnosis

“…Moreover, we did detect potent hemoglobinolytic activity in adult worm extracts at acidic pH values but not at neutral pH (not shown) where Ov -AEP-1 is catalytically active. This is in marked contrast to the ‘hemoglobinase’ sequence from the lung fluke, P. westermani , where the recombinant protein has been reported to digest hemoglobin at acid pH (and not neutral pH) 33. Moreover, the P. westermani AEP is apparently sensitive to the inhibitor of C1 family cysteine proteases, E64, while other AEPs are generally not affected by this inhibitor, responding mainly to inhibitors that complex with free-thiols (http://merops.sanger.ac.uk/index.htm).…”

“…Sm AE is expressed in the gastrodermal epithelial cells of S. mansoni where erythrocytes are lysed and hemoglobinases act to digest hemoglobin for nutrient acquisition 32. In the human lung fluke, Paragonimus westermani , legumain is expressed in the intestinal epithelium of the adult worm 33. Parasitic helminths other than trematodes also express AEPs in their intestines; the blood-feeding nematode that parasitizes sheep, H. contortus , expresses a legumain on the microvillar surface of the intestinal cells of adult worms,16 co-localizing with the sites of expression of other proteinases involved in blood-feeding 34.…”

Characterization and localization of antigens for serodiagnosis of human paragonimiasis

“…There are many different cysteine proteases in Paragonimus , and their tissue localization appears to vary. Prior studies have localized them in the intestinal epithelium (Choi et al 2006 ), esophagus (Yoonuan et al 2016 ), and the tegument in the anterior part of the fluke including the oral sucker (Na et al 2006 ).…”

The Phylogeny, Structure and Function of Trematode Cysteine Proteases, with Particular Emphasis on the Fasciola hepatica Cathepsin L Family

“…74 Immunolocalisation studies have shown that the major cathepsin F proteases of adult C. sinsensis (Cs-CF-4 and Cs-CF-9) and P. westermani are expressed exclusively in the cells lining the gut. 21,26,75 In contrast, the cathepsin F expressed by O. viverrini (Ov-CF-1) has been localised within the gut, vitellaria, testes and eggs of adult worms 22 suggesting a wider role for this protease. Interestingly, the cathepsin Fs expressed and secreted from P. westermani newly excysted metacercariae (PwMc28a and PwMc28b) have been localised to the tegument and anterior border of the oral sucker.…”