Purification of Polyphenoloxidase from the Purple‐fleshed Potato ( <i>Solanum tuberosum</i> Jasim) and its Secondary Structure

Abstract

ABSTRACT: Polyphenoloxidase (PPO) was purified from purple‐fleshed potatoes ( Solanum tuberosum Jasim) using membrane concentration, ammonium sulfate fractionation, Resource Q ion exchange chromatography, and Sephacryl S‐200 HR gel permeation chromatography. PPO was purified 78‐fold from a crude extract. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis results showed that the purified enzyme has a major subunit molecular weight of 40 kDa. To elucidate the secondary structure of the purified PPO, circular dichroism (CD) was performed. The CD spectrum of the purified enzyme showed that PPO contains 35% α‐helix, 30% β‐turn, and 35% random coil structure.