Purification and characterization of phospholipase A2isoforms from the hepatopancreas of red sea bream, Pagrus major¹


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Abstract

Two phospholipase A2(PLA2) isoforms, tentatively denoted as DE-1 and DE-2 PLA2s, were purified from the hepatopancreas of red sea bream (Pagrus major) to near homogeneity by sequential column chromatography on S-Sepharose fast flow, DEAE-Sepharose fast flow and butyl-Cellulofine, and by ion-exchange, gel-filtration and reversed-phase HPLC. The purified DE-1 and DE-2 PLA2s both showed a single band with the apparent molecular mass of approx. 13.5 kDa by SDS-polyacrylamide gel electrophoresis, and were found to be both related to group I PLA2based on the N-terminal amino acid sequences. DE-1 PLA2had a pH optimum in the alkaline region at around pH 10 and required approximately 10 mM of Ca2+and 4-10 mM of sodium deoxycholate for its maximal activity, using 2 mM of phosphatidylcholine and phosphatidylethanolamine as substrates. DE-2 PLA2also had a pH optimum in the alkaline region at around pH 8-9 and required >10 mM of Ca2+and approximately 6 mM of sodium deoxycholate for its maximum activity with 2 mM of phosphatidylcholine as a substrate; its enzymatic activity towards phosphatidylethanolamine was greatly inhibited by the addition of sodium deoxycholate. The results demonstrate that red sea bream hepatopancreas contains two enzymatically distinct group I PLA2isoforms.

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