Lysosomal deoxyribonuclease II from the mussel Mytilus galloprovincialis: Characterization and seasonal activity

Abstract

In view of the importance of Mytilus species in marine ecology and environmental quality assessment, all aspects of mussel enzymes that are related to environmental factors are of great relevance. A lysosomal enzyme, deoxyribonuclease II, a member of the acid deoxyribonucleases, has a major role in cellular DNA degradation. The presence and seasonal variations of the acid deoxyribonuclease (DNase) activity in the digestive gland and gills of the mussel Mytilus galloprovincialis were investigated. The enzyme was localized in the lysosomal vacuolar system of both gill and digestive gland tissues. Two active acid DNase isoforms were detected in the digestive gland (48 and 37 kDa) and one in the gills (48 kDa). All active enzyme isoforms coincided with protein bands immunoreactive to antibodies raised against human DNase II. Post-translational lysosomal processing of acid DNase in the digestive gland but not in the gills indicated tissue-specific enzyme maturation. The activity of acid DNase determined across the annual cycle showed a tissue-specific pattern that could be related to the seasonal activity of mussel organs and their biological function. In the digestive gland, high DNase activity was observed in relation to food availability and spawning. Higher enzyme activity in the gills observed in the autumn/winter period could be associated with feeding and cellular adaptation to low seawater temperatures.