PURIFICATION AND PROPERTIES OF POLYPHENOL OXIDASE FROM OIL BEAN (PENTACLETHRA-MACROPHYLLA BENTH) SEEDS

Polyphenol oxidase extracted from oil bean (Pentaclethra macrophylla) seeds was purified 165-fold over the crude enzyme extract. The apparent molecular weight of the enzyme by gel filtration was 110.8 k +/- 9.0 k while SDS-PAGE indicated a single species of molecular weight 28.0 k. A copper content of 1.9 mg g-1 corresponds to one copper atom for each of the four subunits. The purified enzyme oxidised pyrogallol, catechol, 4-methylcatechol and L-dihydroxyphenylalanine but had low activity towards tyrosine. p-Cresol, caffeic acid and cholorogenic acid were not oxidised. Thio-compounds were strong inhibitors of the enzyme. The phenolic compounds tyrosine, resorcinol and orcinol inhibited catechol oxidation but became oxidised in the process.