Bile salt-activated lipase expression during larval development in the haddock ( Melanogrammus aeglefinus)

In the present work, we report the characterization of the partial cDNA sequence of a bile salt-activated lipase (BAL) cDNA from haddock. The predicted polypeptide encoded by the cDNA sequence contains the bile salt-binding site characteristic of all BALs at amino acid positions 36–45, and the lipid-binding site thus far only reported in fish BALs starting at position 345. Other features of BAL are also present including: the active site serine motif at positions 111–117, the catalytic triad formed by the residues S 114, D 239 and H 358, and an N-glycosylation site at position 107. The relative levels of BAL gene expression were determined in haddock larvae during ontogeny by reverse transcription–polymerase chain reaction (RT–PCR) with the earliest detectable transcript levels identified at hatch. Using in situ hybridization, the BAL transcripts were localized consistently in the pancreas of haddock larvae from mouth opening until 401 degree days (DD). Using biochemical techniques, the specific activity of BAL was found to decline significantly over time. Our results also suggest that haddock larvae are capable of digesting lipids at the time of mouth opening.