Peroxidase from leaves of royal palm tree Roystonea regia: purification and some properties

Screening of tropical plants demonstrated high peroxidase activity in leaves of some species of palms. Using the leaves of royal palm Roystonea regia as a source, the peroxidase has been isolated to homogeneity. The enzyme purification steps included homogenization, (NH₄)₂SO₄ precipitation, extraction of palm leaf colored compounds and consecutive chromatography on Phenyl-Sepharose, Sephacryl S100 and DEAE-Toyopearl. The novel peroxidase was characterized as having a specific activity of 6170 U/mg, RZ 3.0, molecular weight of 51 kDa and isoelectric point pI 3.5. The electronic spectrum of RPP is characteristic for plant peroxidases with a Soret maximum at 403 nm and maxima in a visible region at 492 and 633 nm, respectively. The substrate specificity of royal palm tree peroxidase (RPTP) is distinct from the specificity of other plant peroxidases. The best substrates for RPTP are ferulic acid and 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid). The palm peroxidase exhibits an unusually high thermostability inactivating at 90 °C with k_inac of 1.5×10⁻² min⁻¹.