Investigation of biochemical properties of polyphenol oxidase from broad bean (Vicia faba L.)

ABSTRACT INVESTIGATION OF BIOCHEMICAL PROPERTIES OF POLYPHENOL OXIDASE FROM BROAD BEAN (Vicia faba L.) In this study, the biochemical properties of partially purified polyphenoloxidase from broad bean (Vicia faba L.) were investigated, collected from Antalya Province. It was determined that the broad bean PPO had 2 isoenzymes in native electrophoresis. The substrate of greatest interest for the enzyme was determined as hydrocaffeic acid, followed by 4-methylcatechol and catechol. The optimum temperature value of the enzyme was found to be 30 °C, in the presence of hydrocaffeic acid, 4-methylcatechol and catechol substrates. The optimum pH value of broad bean PFO was determined as 8,0; 4,0 and 4,0 in the presence of hydrocaffeic acid, 4-methylcatechol and catechol substrates, respectively. The Km values of the Broad bean PPO, for hidrocaffeic acid, 4-methylcatechol and catechol substrates were determined 0,172 mM; 7,133 mM and 9.158 mM, by Lineweaver-Burk curve, respectively. When the thermal stability profile of the enzyme was examined, at the end of 10 days, it was observed that, for hydrocaffeic acid substrate the enzyme retained over 77% of its original PPO activity at 30 ºC. IC50 values of ascorbic acid, benzoic acid, sodium azide and sodium metabisulfite, the most common PFO inhibitors, were determined as 8,25 µM; 11,00 mM; 60,00 mM and 116,00 µM, respectively. It was examined that the effect of the Na+, K+, Ba+2, Mg+2, Mn+2, Hg+2, Ni+2, Cu+2, Ca+2 and Fe+2, on the PPO activity, at the 1 mM; 5 mM and 10 mM final concentrations.