Phenoloxidase in the scallop Chlamys farreri: Purification and antibacterial activity of its reaction products generated in vitro

Phenoloxidase (PO) was purified from hemocytes of the scallop Chlamys farreri using native-PAGE and gel permeation column chromatography, and then substrate specificity and antibacterial activity generated from reaction products of purified PO were analyzed. The results showed purified PO had a molecular mass of 576 kDa in native-PAGE and 53 kDa in denatured PAGE, and could catalyze the substrates L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine, catechol and hydroquinone suggesting it is a type of p-diphenoloxidase. Using dopamine as a substrate, PO reaction products significantly inhibited the growth of Vibrio alginolyticus, Vibrio parahaemolyticus and Aeromonas salmonicida. No significant inhibition was found in Streptococcus dysgalactiae, Streptococcus iniae, Micrococcus lysodeikticus and Edwardsiella tarda. When L-DOPA was used as a substrate, significant inhibition occurred in A. salmonicida only.

► Phenoloxidase (PO) was purified from Chlamys farreri.
► C. farreri PO is a type of p-diphenoloxidase with an appearance of aggregate.
► It is PO reaction products not PO have the antibacterial activity.
► PO reaction products showed strong inhibition in Vibrio and Aeromonas.
► PO reaction products had no effects on Streptococcus, Micrococcus and Edwardsiella.