Purification and characterization of cell wall-bound peroxidase from vanilla bean

A cold-active ionically bound cell wall peroxidase was purified from a polyvinylpolypyrrolidone extract of mature vanilla beans by ultra filtration of 10 kDa and gel filtration chromatography on Sephacryl S-200. The M, was 46.5 kDa determined by electrophoresis on SDS-PAGE, while native gel filtration confirmed tetramer enzyme form of approximately 186 kDa. The optimum pH and temperature were 3.8 and 16 degrees C, respectively, as determined with guaiacol as the substrate (Km 3.8 mmol/L). The pI was approximately 7.7. The POD was inhibited by 1,4-dithiothreitol, beta-mercaptoethanol and sodium azide. The POD showed decreasing activity in the presence of ascorbic acid, NaEDTA and sodium dodecyl sulfate at 1 mmol/L. The enzyme lost 80% of its activity in the presence of 20% ethanol. These results will permit better understanding of POD role in vanilla curing process. (C) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.