Characterisation and expression of secretory phospholipase A2 group IB during ontogeny of Atlantic cod ( Gadus morhua)

Abstract

The pancreatic enzyme secretory phospholipase A2 group IB (sPLA2 IB) hydrolyses phospholipids at the sn-2 position, resulting in a NEFA and a lyso-phospholipid, which are then absorbed by the enterocytes. The sPLA2 IB is a member of a family of nineteen enzymes sharing the same catalytic ability, of which nine are cytosolic and ten are secretory. Presently, there are no pharmacological tools to separate between the different secretory enzymes when measuring the enzymatic activity. Thus, it is important to support activity data with more precise techniques when isolation of intestinal content is not possible for analysis, as in the case of small teleost larvae, where the whole animal is sometimes analysed. In the present study, we characterise the sPLA2 IB gene in Atlantic cod (Gadus morhua) and describe its ontogeny at the genetic and protein level and compare this to the total sPLA2 activity level. A positive correlation was found between the expression of sPLA2 IB mRNA and protein. Both remained stable and low during the larval stage followed by an increase from day 62 posthatch, coinciding with the development of the pyloric ceaca. Meanwhile, total sPLA2 enzyme activity in cod was stable and relatively high during the early stages when larvae were fed live prey, followed by a decrease in activity when the fish were weaned to a formulated diet. Thus, the expression of sPLA2 IB mRNA and protein did not correlate with total sPLA2 activity.