• The Korean Journal of Pharmacology
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• v.25 no.1
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• pp.75-85
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• 1989

In opsonized zymosan activated PMN leukocytes, N-ethylamleiamide and $Hg^{++}$, penetrable sulfhydryl group inhibitors, inhibited superoxide generation, NADPH oxidase activity and lysosomal enzyme (lactic dehydrogenase and ${\beta}-glucuronidase$) secretion. P-Chloromercuribenzoic acid and p-chloromercuribenzenesulfonic acid, surface sulfhydryl group inhibitors did not affect superoxide generation but effectively inhibited both NADPH oxidase activity and lysosomal enzyme secretion. During phagocytosis, contents of surface and soluble sulfhydryl groups were gradually decreased with increasing incubation times. N-ethylmaleiamide and $Hg^{++}$ caused a loss of both surface and soluble sulfhydryl groups. P-Chloromercuribenzoic acid and p-chloromercuribenzenesulfonic acid significantly decreased the surface sulfhydryl content but did not after soluble sulfhydryl groups. Cysteine and mercaptopropionylglycine inhibited superoxide generation and lysosomal enzyme secretion. Glutathione had no effect on superoxide generation but remarkably inhibited lactic dehydrogenase release. Suppression of superoxide generation by N-ethylmaleiamide was reversed by cysteine and mercaptopropionyl-glycine but not by glutathione. Inactivation of NADPH oxidase by N-ethylmaleiamide was prevented by glutathione, cysteine or mercaptopropionylglycine. Stimulated superoxide generaion by carbachol was completely abolished by N-ethylrnaleiamide and antagonized by atropine. Thus, the expression of PMN leukocyte response to external stimuli may be associated with the change of sulfhydryl groups content. It is suggested that lysosomal enzyme secretion is influenced by both surface and soluble sulfhydryl groups, whereas superoxide generation by intracellular soluble sulfhydryl groups.

• Parasites, Hosts and Diseases
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• v.56 no.5
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• pp.409-418
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• 2018

Acanthamoeba spp. are free-living protozoa that are opportunistic pathogens for humans. Cysteine proteases of Acanthamoeba have been partially characterized, but their biochemical and functional properties are not clearly understood yet. In this study, we isolated a gene encoding cysteine protease of A. castellanii (AcCP) and its biochemical and functional properties were analyzed. Sequence analysis of AcCP suggests that this enzyme is a typical cathepsin L family cysteine protease, which shares similar structural characteristics with other cathepsin L-like enzymes. The recombinant AcCP showed enzymatic activity in acidic conditions with an optimum at pH 4.0. The recombinant enzyme effectively hydrolyzed human proteins including hemoglobin, albumin, immunoglobuins A and G, and fibronectin at acidic pH. AcCP mainly localized in lysosomal compartment and its expression was observed in both trophozoites and cysts. AcCP was also identified in cultured medium of A. castellanii. Considering to lysosomal localization, secretion or release by trophozoites and continuous expression in trophozoites and cysts, the enzyme could be a multifunctional enzyme that plays important biological functions for nutrition, development and pathogenicity of A. castellanii. These results also imply that AcCP can be a promising target for development of chemotherapeutic drug for Acanthamoeba infections.

• BMB Reports
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• v.40 no.5
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• pp.636-643
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• 2007

This study was designed to identify and characterize the mechanism of macrophage activation by AAP, an acidic polysaccharide fraction isolated from the roots of Angelica sinensis (Oliv.) Diels. As a result, AAP significantly enhanced nitric oxide (NO) production and cellular lysosomal enzyme activity in murine peritoneal macrophages in vitro and in vivo. Furthermore, L-NAME, a specific inhibitor of inducible nitric oxide synthase (iNOS), effectively suppressed AAP-induced NO generation in macrophages, indicating that AAP stimulated macrophages to produce NO through the induction of iNOS gene expression and the result was further confirmed by the experiment of the increase of AAP-induced iNOS transcription in a dose-dependent manner. To further investigate, AAP was shown to strongly augment toll-like receptor 4 (TLR4) mRNA expression and the pretreatment of macrophages with anti-TLR4 antibody significantly blocked AAP-induced NO release and the increase of iNOS activity, and tumor necrosis factor-$\alpha$ (TNF-$\alpha$) secretion.