Process Biochemistry, Vol.91, 65-72, 2020
Molecular cloning and characterisation of a novel xanthine oxidase from Cellulosimicrobium cellulans ATCC21606
Xanthine oxidase (XOD) catalyses the oxidation of hypoxanthine into xanthine and xanthine into uric acid. The enzyme plays a key role in the purine metabolic pathway. Despite the presence of different XODs in prokaryotes, the functional and structural knowledge of prokaryotic XODs remain limited (compared with their well-known eukaryotic counterparts), thereby hindering their biochemical analysis and industrial application. Using genetic and biochemical analyses, we identified and characterised recombinant XOD (CcXOD(AB)) from Cellulosimicrobium cellulans ATCC21606. Bioinformatics analysis suggests that CcXOD(AB) shares low amino acid sequence identities with other XODs. The purified enzyme exhibits the maximum activity at 55 degrees C and pH 8.0. In addition, CcXOD(AB) exhibits moderate thermostability and retains 80.65 % of the original activity after 30 min of incubation at 60 degrees C. Ca2+ has a slight inhibitory effect, whereas Co2+ and Mn2+ have a strong inhibitory effect on XODAB activity. In particular, low Ba2+ and Mg2+ concentrations have no effect, whereas high Mg2+ (>= 10 mM) and Ba2+ (>= 2 mM) concentrations show an inhibitory effect on enzyme activity. The K-m and V-max values for xanthine are 131.29 +/- 11.09 mu mol.L-1 and 15.23 +/- 0.65 mu mol.L(-1)min(-1), respectively. Results indicate that CcXOD(AB) is a novel enzyme with potential industrial application.