Purification and characterization of polyphenol oxidase from unripe almond (Prunus dulcis) plant

Polyphenol oxidase (PPO) of unripe almond (Prunus dulcis) fruit was extracted and purified through (NH4)2SO4 precipitation, dialysis, gel filtration. The sample obtained from ammonium sulfate precipitation and dialysis was used for characterization of the PPO. For this aim, optimum conditions, i.e. pH, temperature were determined with different with substrates. The best substrate of the PPO was found to be 4-methyl catechol. Optimum pH and temperature were found 6,5 and 35oC for this substrate. Km and Vmax values were 1,71 mM and 99,0 ?A dak-1 with 4-methyl catechol, respectively. Seven inhibitors were tested in the study and the effectives were found to be sodium azide, benzoic acid, citric acid, L-ascorbic acid and tiourea as competitive inhibitors. The enzyme activity was also tested against some metals. Fe+3, Cu+2, Mn+4, and Pb+2 ions act as enzyme activator however Mg+2, Ba+2, Ca+2, Co+3, Sn+2, K+1 and Sn+2, metals act as enzyme inhibitors.