Abstract:

Study on extraction and physical-chemical properties of Laccase (EC 1.10.3.2) from Eriobotrya japonica pulp, in order to establish the foundation for discussion on flesh woodiness mechanism of laccase in loquat fruits under low temperature storage. Laccase in Eriobotrya japonica Lindl. ‘Jiefangzhong’ was extracted and purified by (NH4)2SO4 salting out, dialysis and DEAE-cellulose column chromatography. The influences of different temperature, pH, substrate, inhibitor and metal ions on the activity of laccase were studied. The changes of pH were determined in loquat fruits during storage. The results showed that the optimal temperature of laccase was 4.4, and optimal pH was 45℃. The enzyme activity was stable in the pH range of 3.2-4.4. The laccase activity was increased by the addition of Cu2+ and K+, while it was inhibited by the addition of Ag+, Fe2+ and Fe3+. Both EDTA and L-cysteine had an inhibitory effect on the laccase activity, and L-cysteine was the strongest one. The Km constants based on the substrate of 2,2-azobis(3-ethylbenzothiazole-6-sulfonaic acid) (ABTS) was 0.00512 mol/L .