PARTIAL PURIFICATION AND CHARACTERIZATION OF POLYPHENOL OXIDASE FROM ARAUCARIA ANGUSTIFOLIA (BERT, O. KTZE) SEEDS

Polyphenol oxidase (PPO) from Araucaria angustifolia seeds (pinhao) was extracted and partially purified by ammonium sulfate precipitation and gel-filtration chromatography, appearing as a single band on zymogram analysis. The partially purified enzyme showed optimal activity at 30-35C and pH 5.0 using catechol as substrate. PPO activity was stimulated by FeSO4, ZnSO4 and AlCl3, and was moderately inhibited by NiCl2 and MgCl2. The addition of CaCl2 and CuSO4 showed no effect. Ascorbic acid and cysteine moderately inhibited pinhao PPO. The enzyme was slightly inhibited by sodium metabisulfite, beta-mercaptoethanol, citric acid and ethylenediaminetetraacetic acid, whereas the addition of sodium dodecyl sulfate completely inhibited PPO activity. To our awareness, this is the first report on the characterization of pinhao PPO. PRACTICAL APPLICATIONS Araucaria angustifolia seeds (pinhao) are starch-rich, and are considered as an alternative starch source to be utilized by the food industry. However, the external and internal seed coats are difficult to remove. Particularly, the internal coat is adhered to the seed and has a high phenolic content, and the incomplete removal of this coat might lead to the production of starch with undesirable brown color. Because polyphenol oxidases (PPOs) are enzymes related to the browning of plant products through the utilization of phenolic compounds as substrates, the knowledge on the properties and characteristics of pinhao PPO might be valuable in controlling the enzyme activity during production of starch or other related products which utilize raw pinhao seeds.