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Enzymatic characterization of a laccase from lychee pericarp in relation to browning reveals the mechanisms for fruit color protection

Zhang, X., Fang, F., He, Q., Zhang, X., Shi, N., Song, J., Zhang, Z., Pang, X. (2018). Enzymatic characterization of a laccase from lychee pericarp in relation to browning reveals the mechanisms for fruit color protection, 42(2), http://dx.doi.org/10.1111/jfpp.13515

Abstract

© 2017 Wiley Periodicals, Inc. An anthocyanin degradation-related laccase (LcADE/LAC) from lychee fruit was found to be responsible for the pericarp browning. In this study, LcADE/LAC was purified and characterized for better control of laccase-based browning. The optimum pH for LcADE/LAC activities was 5.0–6.0, with less than 20% of the activity retained at pH 3.0. The optimum temperature is 45 °C, and the activity is thermostable at this temperature. The enzyme was inhibited by 1 mM Fe2+, but induced by 0.1 mM Fe3+. Na2SO3 and l-cysteine highly inhibited the activity at 0.1 mM, while kojic and phytic acids inhibited 40 and 43%, respectively, at 1 mM. Na2SO3 inhibited the activity in a noncompetitive model with a Ki value of 33.1 μM, and the inhibition increased when pH decreased to 3.5. In postharvest fruit, the enzyme activity and LcADE/LAC gene expression were strongly inhibited by SO2-HCl treatment. Practical applications: The present study systematically characterizes a pericarp browning related laccase (LcADE/LAC) from lychee. The high sensitivity of the enzyme to low pH and several inhibitors, such as SO2, l-cysteine, and kojic acid and phytic acids, will help in the development of more efficient strategies for browning control of lychee pericarp or other laccase-based food browning.

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