L-Amino Acid Oxidase from Marine Bacterium: Purification, Characterization and Evaluation of its Anticancer and antioxidant activities

L-amino acid oxidases (LAAO) are extensively distributed in nature and active on most proteinogenic L-amino acids. Dehydrogenation of such amino acids produces α-keto acids and hydrogen peroxide which act as oxidative, antimicrobial and antitumor agents. In the presented work, biochemical characterization of L-amino acid oxidase from newly isolated marine bacterium Bacillus velezensis was performed. The molecular mass of the purified LAAO was 120 kDa which demonstrated homodimer nature with 60 kDa subunits by SDS-PAGE electrophoresis. Size exclusion chromatography was applied to achieve a purified enzyme with specific activity of 868.15 U/mg which represents 2.46-fold higher than the crude enzyme. Maximum enzyme activities were obtained at pH 8.4, 40°C while the enzyme showed a stability for 1 h over pH range 6-9 and 40°C. The values of Michalis parameters were calculated as Km value of 0.312 mM L-Leucine with corresponding Vmax of 19.87 U/mg. Finally, the purified LAAO was investigated an anticancer property towards different types of tumors. This objective was accomplished through measuring cytotoxicity of HepG2 and Caco-2 cancer cell lines and also through measuring the antioxidant activity. The findings indicated that LAAO individually was able to induce a cytotoxic effect by reducing the percentage of cell viability to 81% in HepG2 and Caco-2 cancer cell lines. Investigations of the antioxidant activity of LAAO showed a potent antioxidant activity. LAAO showed the ability to scavenge 1,1-diphenyl-2-pycryl-hydrazyl (DPPH) when compared with the ascorbic acid (vitamin C), a highly potent antioxidant agent. These results are promising for enzyme harnessing in different pharmaceutical and biotechnological application.