Biochemical Properties of Emir Grape Polyphenol Oxidase as Affected by Harvest Year

Abstract

Abstract.Effect of harvest year on biochemical properties of polyphenol oxidase (PPO) from Narince grapes was studied in 2006 and 2007.The optimum pH of the enzyme in both years were found to be 5.49 whereas optimum temperature for enzyme activity was 30°C in the year 2006 and 35°C in the year 2007. The apparent substrate specificities were established from V max /K m as: caffeic acid > 4-methylcatechol >catechol >pyrogallol for two enzymes in both years. There were marked differences between the two enzymes in terms of thermal stability. The effects of inhibitors varied in a dose dependent manner and according to the harvest year.