L-Amino acid oxidase fromCerastes viperasnake venom: Isolation, characterization and biological effects on bacteria and tumor cell lines

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A homodimeric L-amino acid oxidase enzyme (Cv-LAAOI) was isolated from the venom of Cerastes vipera (Egyptian Sand viper) using gel filtration followed by anion exchange chromatography. The molecular mass of Cv-LAAO is 120 kDa in its native form and 60 kDa in its monomeric form. The optimum enzyme activity was achieved on L-Leucine as a substrate in 50 mM buffer pH 7.5 at 50 °C. The Cv-LAAOI activity was significantly reduced by increasing the temperature over 40 °C, lost 75% of its activity at 60 °C and inhibited completely at 80 °C. The Cv-LAAOI attains the highest substrate specificity towards L-Met. The results have also indicated that Mn2+ enhances the enzyme activity by 10%, while Cu2+, Hg2+, Ni2+, Co2+ have suppressive effects on the Cv-LAAOI activity. On the other hand, EDTA has no significant effect on the enzyme activity. The kinetic parameters of Cv-LAAOI activity (Km, Kcat and Vmax) estimated on L-Leucine at pH 8 and 37 °C were found to be 2 mM, 12 S−1 and 16.7 μmol/min/ml, respectively. In addition, the results have shown that Cv-LAAOI exhibits a significant bactericidal activity against gram-positive and gram-negative bacteria, particularly Staphylococcus aureus and Escherichia coli with MIC values of 20 μg/ml. Moreover, Cv-LAAOI has exhibited a considerable cytotoxic activity against breast cancer cell line (MCF-7) with IC50 value 2.75 ± 0.38 μg/ml compared with different tumor cell lines (liver HepG2, lung A549, colon HCT116 and prostate PC3). Furthermore, Cv-LAAOI has triggered antiproliferative activity via extensive H2O2 generation as indicated by the increase in H2O2 and TBARS levels accompanied by the depletion in the catalase activity (CAT) in MCF-7 treated cells compared to the untreated ones. Thus, these findings clearly indicate that Cv-LAAOI has a selective cytotoxic effect on breast cancer cell line, demonstrating a great prospective for future use in cancer therapy.HighlightsA novel homodimeric Cv-LAAOI enzyme with a molecular mass of 60 KDa was isolated from Cerastes vipera venom.The CV-LAAOI enzyme is optimally active at pH 7.5 and 50 °C using L-Leucine as a substrate.Cv-LAAOI enzyme displays bactericidal activity against gram-positive and gram-negative bacteria.Cv-LAAOI enzyme exhibits selective cytotoxic effect on MCF-7 breast cancer cell lines.This study sheds a light on the potential effect of snake venom L-amino acid oxidase in cancer treatment.

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