Partial purification and characterization of polyhenol oxidase from thermophilic Bacillus sp.

Abstract

Polyphenol oxidases are enzymes that catalyze the oxidation of phenolic compounds using molecular oxygen. The ability of polyphenol oxidases to act on phenolic compounds makes them highly useful biocatalysts for various biotechnological applications. They are commonly found in animals, plants and fungi. Recent genome analysis have shown that polyphenol oxidases are also widespread in bacterial species. In this study, detection, partial purification and characterization of polyphenol oxidase from thermophilic Bacillus sp., which was isolated from a geothermal region was achieved. The samples from bacterial culture were boiled and compared with not boiled ones in order to prove the existence of enzyme in bacterium. The existence was also supported with the appearance of dark bands on polyacrylamide gel after staining with catechol solution. Results of activity staining and activity measurements of samples from intracellular and extracellular extract revealed that the enzyme was intracellular. Partial purification was performed by acetone precipitation and gel filtration chromatography with 35% yield and 1.24 purification fold. Characterization studies indicated that the enzyme showed highest activity at pH 7.0 and 60C, was stable at temperatures between 30 and 60C and more than 80% of activity was retained in the pH range of 5-8. The results of agent and metal ion effect on enzyme activity revealed that the enzyme was totally inhibited in the presence of DTT and sodium diethyldithiocarbamate and highly activated with copper ions whereas other agents or metal ions did not have significant effect on activity. Km and Vmax values for the enzyme were determined as 91mM and 2.25 .abs/min/ml, respectively.