Diphenolases from two cultivars of cherry laurel (Laurocerasus officinalis Roem.) fruits at an early stage of maturation

摘要

Diphenolases from two cherry laurel cultivars (Laurocerasus officinalis Roem. 'Globigemmis' and 'Oxygemmis') were highly ac tive against 3-(3,4-dihydroxyphenyl)propionic acid (DHPPA) at acidic pH values with temperature optima of 50 and 40℃, respec tively. Although the pH-stability profiles showed that both enzymes were fully stable at pH 7.0, their stabilities decreased significantly at alkaline pH values. Thermal-stabilities of the cherry laurel diphenolases indicated that enzymes from the two culti vars share similar thermodynamic properties and heat-sensitivities as a result of heat-inactivation. In addition, ascorbate and me tabisulfite, at 1 mM final concentrations, almost completely inhibited the oxidation of DHPPA by the enzymes, indicating the sensitivities of the cherry laurel diphenolases from the two cultivars towards general Polyphenol oxidases inhibitors. It can be con cluded that the crude enzymes prepared from the cherry laurel fruits of the two cultivars, at an early stage of development, possess diphenolase activities sharing similar behaviours.