Abstract:In this study, the polyphenoloxidase (PPO) was extracted using the homogenate extraction from Solenocera crassicornis (S. crassicornis) in the East China Sea, and purified through ammonium sulphate precipitation, ion-exchange and gel filtration. The substrate specificity (L-dihydroxyphenylalanine (L-DOPA) as the substrate) and kinetic properties of the purified PPO, along with the effects of different inhibitors and metal ions on the PPO, were determined. The obtained results showed the optimal conditions for the homogenate extraction were: the material to liquid ratio 1:2 (W/V), pH 7.5, time 3 h, and temperature 50 ℃. The yield and purification factor were 1.2% and 25.9, respectively. This PPO significantly catalyzed the oxidation of L-DOPA and catechol (p≤0.05), with the Km values being 3.8 mM and 8.12 mM, respectively, indicating that the PPO belongs to the catechol enzyme family. The PPO was sensitive to phenylthiourea, ascorbic acid, and citric acid, and its activity was strongly inhibited by Cu2+, Zn2+, and ethylenediaminetetraacetic acid (EDTA). Thus, the PPO from S. crassicornis could be a metalloenzyme containing Cu2+ in its active center. The results of this study provide the basis for controlling the melanotic blackening of S. crassicornis.
