ANALYSIS OF LYCHEE POLYPHENOL OXIDASE ACTIVITY UNDER DIFFERENT CONDITIONS

Lychee polyphenol oxidase was purified by ammonium sulfate fractionation,gel fiLtration and ion exchange chromatography. The enzyme was found to be homogenous by SDSP-AGE and shown to be activated by divalent canons such as Mn²⁺ and Ca²⁺ and long chainfatty acids,especially those with a high degree of unstaturation,and was markedly inhibitedby FeSO₄ and SnCl₂ and short chain fatty acids such as butyric acid using 4-methylcatechol assubstrate. Aslight decrease or increase was observed by added sodium dodecyl sulfate(SDS), hexadecyltri-methylammonium bromide (CATs) or triton X-100, respectively. Furthermore the effect of divalent cations on the activity of polyphenol oxidase was analysed.The optimum conditions for the activation process produced by the divalent canons had beenexamined with respect to canon concentration and pll of the reaction medium. This activationhad also been studied with regard to the kinetic parameters of the enzyme,which half-activation constants were in the order of 0. 8 mmol/L for Mn²⁺ and 1. 2 mmol/L for Ca²⁺. The K_m decreased and the V_max increased when Mn²⁺ and Ca²⁺ (5 mmol/L) were present.