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    • sennoside Arginases from several species and tissues

    2023-01-16

    Arginases from several species and tissues have been found to be inhibited by amino acids [51]. In the present study, monocarboxyilic amino acids with five or more carbon atoms such as ornithine, lysine, valine, leucine and isoleucine inhibited CL-ARG. The results revealed that as the amino sennoside concentration increased in the assay reaction mixture the remaining enzyme activity decreased. The Linweaver-Burk plots revealed that all the tested amino acids were competitive inhibitors for CL-ARG. The competitive inhibition would be explained by a conformational change induced by the substrate arginine which prevents the binding of the inhibitor to the enzyme. The existence of allosteric sites on arginase molecule has been suggested for the enzyme from bovine liver [52], human liver [53], rat kidney [54] and rat liver [55]. In parallel with arginase buffalo liver [25], ornithine and lysine caused competitive inhibition like CL-ARG. Finally, this work represents a reproducible and simple method for CL-ARG purification from the camel liver cytosol as a locally available rich source in Egypt for medical and industrial purposes. Cheng et al. [56] and Lam et al. [57] showed that the application of pegylated recombinant human arginase I (rhArg-PEG) either alone or in combination with chemotherapeutic drugs might represent a specific and effective therapeutic strategy against advanced hepatocellular carcinoma (HCC). They suggest that rhArg-PEG is a good candidate for the treatment of HCC, whose anti-cancer activity is mediated by the depletion of arginine, resulting in a cell cycle arrest in HCC cells. They developed a recombinant form of human ARG I, covalently modified with polyethylene glycol (PEG) via a succinimidyl propionate (SPA) linker. Pegylation greatly increased the enzyme’s half-life without affecting its sennoside enzymatic activity. The prepared rhArg-PEG inhibited the proliferation of HCC cell lines (HepG2, Hep3B, PLC/PRF/5, Huh7 and SK-HEP-1). Towards industrial applications, a great demand exists for L-ornithine production as nutritional supplement and pharmaceutical preparation via its enzymatic production using ARG enzyme [58], [59], [60], [61].
    Conclusion The current study provides strong evidence to support the hypothesis that the molecular and the kinetic differences of CL-ARG reflect the unique natural history and the environmental habitat of camel towards other species. The current findings, for the first time, demonstrate a similarity of the purified CL-ARG towards other species in some properties but differ in their chromatographic behaviour on the cation exchanger column, molecular weight, oligomeric protein structure, pI, Km, and optimum temperature. Our results provided valuable information for determining the optimal conditions for the production of purified arginase from camel liver to fulfill the demands of medical and industrial applications.
    Conflict of interests
    Introduction Nitric oxide (NO) is a free radical that plays a role in the host defensive response to infection in oral tissues and is synthesized from the conversion of L-arginine to L-citrulline by nitric oxide synthase (NOS) (Uğar-Cankal & Ozmeric, 2006). Although NO has beneficial effects, including antimicrobial activity and immune modulation (Allaker, Silva Mendez, Hardie, & Benjamin, 2001), it is also regarded as harmful because of its cytotoxic or cytostatic actions, such as stimulation of the release of proinflammatory mediators, which include peroxynitrite, interleukin-6, tumor necrosis factor, and interferon gamma and are capable of stimulating NO production in bone cells (Gaspirc, Masera, & Skaleric, 2002). NO affects bone cell function, bone maintenance, and bone remodeling (van’t Hof & Stuart, 2001). NO, which is produced by osteocytes, is an important regulator of bone response to loading and has been shown to mediate osteoclast activity. NO metabolism is associated with the clinical inflammatory state of peri-implant tissues. In inflamed peri-implant tissues, its levels were found to be higher than in healthy sites (Tözüm et al., 2005). It is also affected by the loading of dental implants (Güncü, Tözüm, Güncü, Yamalik, & Tümer, 2009). Mechanical stimulus, one of the factors involved in the bone remodeling process around implants (Klein-Nulend, Bacabac, & Mullender, 2005), stimulates NO production (Turner, Takano, Owan, & Murrell, 1996).