Selected Properties of Polyphenol Oxidase Obtained from Ispir Sugar Bean

Polyphenol oxidase enzyme was isolated from Ispir sugar bean by ammonium sulphate precipitation and its biochemical properties were investigated. For this purpose, K-M and V-max values for optimum conditions of pH, temperature, and ionic strength were determined for catechol, catechin, and chlorogenic acid as substrates. Enzyme activities were measured spectrophotometrically at 420 nm using the same substrates at optimum conditions. K-M values were found to be 2.4875, 1.3154, and 2.2487 M for catechol, catechin, and chlorogenic acid, respectively. V-max values were 3.1480, 0.6130, and 0.5039 EU/ml.min for the same substrates, respectively. These results indicated that catechol was used as a subsrate for inhibition studies. For catechol substrate, dithiothreitol, glutathione, thiourea, and L-cysteine chlorid were inhibitors. For these inhibitors, K-i constants were calculated from Lineweaver-Burk plots and inhibiton types were estimated. Moreover, I-50 values were also determined. The most effective inhibitor was found to be glutathione.