Cyanobacterium Oscillatoria sp. peroxidase active at alkaline pH and high stability under chemical stresses

Cyanobacterial peroxidase enzyme extracted from Oscillatoria sp. SWU121 was purified from crude extract by 20-80% ammonium sulfate precipitation, DEAE cellulose ion-exchange chromatography, and Sephadex G-100 size exclusion chromatography. The purified Oscillatoria sp. peroxidase (OsPOX) exhibited a specific activity of 6106.63 mmol.min-1.mg.protein-1, while purification fold and yield were 17.45 and 34.70%, respectively. The OsPOX showed single band of protein on native and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). The molecular weight was 45 kD similarly determined by gel filtration and SDS-PAGE suggesting that the OsPOX contained only one subunit. The apparent Km and Vmax values of the enzyme against phenol were 930 mM and 8078.25 mmol.min-1.mg protein-1, respectively. The temperature and pH optimum for OsPOX were 30ºC and pH 9.0, respectively. However, it was stable at 10 – 70ºC and pH 7.0 - 11.0. The presence of metal ions such as Na+ , Mn2+and Fe3+ enhanced peroxidase activity. On the other hand, Zn+ , Cd2+ and Hg2+ strongly inhibited the enzyme activity. SDS and EDTA reduced the peroxidase activity at 10 mM (20%). The OsPOX was found to be stable in the presence of urea. The affinity of the enzyme was highest for gallic acid, followed by ascorbic acid, phenol and cafeic acid. This finding showed that OsPOX was active at alkaline pH and stable in presence of urea.