Expression analysis and enzymatic characterization of phospholipase Cδ4 from olive flounder (Paralichthys olivaceus)

Phospholipase Cδ4 (PLCδ4) plays a significant role in cell proliferation, tumorigenesis, and in an early stage of fertilization. Despite the characterization of the mammalian PLCδ4, extensive study in aquatic organisms has not been carried out so far. Here, we performed the molecular and biochemical characterization of flatfish Paralichthys olivaceus PLCδ4 (PoPLCδ4) to understand its enzymatic properties and physiological functions. The olive flounder PLCδ4 cDNA has an open reading frame (ORF) of 2,268 bp, and encodes a 755 amino acid polypeptide with a predicted molecular weight of 86 kDa. All the characteristic domains found in mammalian PLCδ isoforms (PH domain, EF hands, an X-Y catalytic region, and a C2 domain) were found to be present in PoPLCδ4. The mRNA expression analysis of PoPLCδ4 showed that PoPLCδ4 is predominantly expressed in the brain, eye and heart tissues. Like other mammalian PLCδ proteins, the enzyme activity of recombinant PoPLCδ4 to phosphatidylinositol-4,5-bis-phosphate (PIP2) was noted to be concentration- and Ca(2+)-dependent. The structural features and biochemical characteristics of PoPLCδ4 were found to be similar to those of mammalian PLCδ4. This is the first demonstration of the expression analysis and enzymatic characterization of piscine PLCδ4.