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  • LAP locations in the parasite tissues

    2023-09-16

    LAP locations in the parasite tissues would provide clues for the potential physiological roles of it inside the parasite body. To date, tissue localization of LAPs has been carried out in many helminth parasites; however, information regarding LAPs in tapeworm is scarce. It was shown that LAPs were extensively distributed in the tissues of adult flukes (Acosta et al., 2008, Changklungmoa et al., 2012, Kang et al., 2011), and associated with the final digestion of absorbed Hb-derived dipeptides from the host (Maggioli et al., 2011). In S. mansoni or S. japonicum, the LAP enzyme has been thought to be a major constituent of eggs and contributed to the egg hatching process (Abouel-Nour et al., 2005, Xu and Dresden, 1986). The aminopeptidase activity also exists in the muscle, reproductive tissue, and intestines of adult nematode parasites and its function is involved in molting, nutrition and embryogenesis (Pokharel et al., 2006, Rhoads and Fetterer, 1998). Our results showed that TpLAP was localized beneath the body wall, mainly in the subtegumental parenchyma zone and uterine wall of adult worms. The periphery of mature eggs was not stained, which differed from S. mansoni eggs as described by Abouel-Nour et al. (2005). In addition, LAPs are rich in the muscle tissues of vertebrata, and influence mostly the production of free PU-WS13 and muscle autolysis (Nishimura et al., 1990). Particularly, some free amino acids, such as leucine and threonine, are essential components and factors required to initiate and maintain metabolism and development of parasites (Ando et al., 1980). Following larval invasion of T. pisiformis in the definitive hosts (commonly dogs), the parasite undergoes transformation from larva to adult with complex morphological and biochemical changes. During the larva-to-adult metamorphosis, a remarkable change is the rapid strobilus development. Therefore, it is implied that TpLAP plays a specific function during protein anabolism leading to the promotion of worm segment development, movement, maturation and elongation of the strobila. In summary, we identified, for the first time, a LAP gene from adult T. pisiformis. The recombinant TpLAP was prepared and enzymatic activity, biochemical properties, and immunolocalization were characterized. These results revealed that TpLAP could be classified into the M17LAP family and that it is a stage-differentially expressed protein. Our findings provide new insights into the study of the mechanisms of the growth, development, and survival of T. pisiformis in the final host and TpLAP has potential value as an attractive target for drug therapy or vaccine intervention.
    Ethics statement The larval and adult Taenia pisiformis used in this study were obtained from infected experimental rabbits and dogs at the Laboratory Animal Center of Lanzhou Veterinary Research Institute, China. The experimental animal protocol was carried out in accordance with the recommendations of the Animal Ethics Committee of Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences.
    Acknowledgments This work was supported by grants from the National Natural Science Foundation of China (grant number 31772726).
    Introduction Aminopeptidases (APs) catalyze the release of amino acid residues from the N-terminal end of peptides and proteins, and are common in microorganisms such as yeasts (Klionsky et al. 1992; Moudni et al. 1995), fungi (Sattar et al. 1989; Nishiwaki and Hayashi 2001), and bacteria (Izawa et al. 1997; Story et al. 2005). Various APs from the yeast, Saccharomyces cerevisiae, have been reported (Matile et al. 1970; Metz and Röhm 1976; Achstetter et al. 1982; Yasuhara et al. 1994). APs are being produced on an industrial scale for use as food additives. Typical sources of APs as food additives are fungi such as Aspergillus (Nakadai et al. 1973) and bacteria such as Bacillus (Minamiura et al. 1969) and Lactobacillus (Choi et al. 1996). However, these AP preparations generally contain proteinases that can hydrolyze proteins randomly, impacting the physical properties of the processed food. Furthermore, the peptides in the hydrolyzate impart a bitter taste, which limits the use of hydrolyzate in the food processing industry. It is well known that those bitter peptides contain hydrophobic amino acid (Matoba et al. 1969), especially on the N- or C-terminal of peptides. Grifola frondosa AP can efficiently reduce bitterness by releasing N-terminal hydrophobic amino acids from bitter peptides (Nishiwaki and Hayashi 2001; Nishiwaki et al. 2002).