Biochemical characterization, cloning and molecular modeling of a digestive lipase from red seabream (Pagrus major): Structural explanation of the interaction deficiency with colipase and lipidic interface

Comparative Study of the Molecular Characterization, Evolution, and Structure Modeling of Digestive Lipase Genes Reveals the Different Evolutionary Selection Between Mammals and Fishes

Vertebrates need suitable lipases to digest lipids for the requirement of energy and essential nutrients; however, the main digestive lipase genes of fishes have certain controversies. In this study, two types of digestive lipase genes (pancreatic lipase (pl) and bile salt-activated lipase (bsal)) were identified in mammals and fishes. The neighborhood genes and key active sites of the two lipase genes were conserved in mammals and fishes. Three copies of PL genes were found in mammals, but only one copy of the pl gene was found in most of the fish species, and the pl gene was even completely absent in some fish species (e.g., zebrafish, medaka, and common carp). Additionally, the hydrophobic amino acid residues (Ile and Leu) which are important to pancreatic lipase activity were also absent in most of the fish species. The PL was the main digestive lipase gene in mammals, but the pl gene seemed not to be the main digestive lipase gene in fish due to the absence of the pl gene sequence and the important amino acid residues. In contrast, the bsal gene existed in all fish species, even two to five copies of bsal genes were found in most of the fishes, but only one copy of the BSAL gene was found in mammals. The amino acid residues of bile salt-binding sites and the three-dimensional (3D) structure modeling of Bsal proteins were conserved in most of the fish species, so bsal might be the main digestive lipase gene in fish. The phylogenetic analysis also indicated that pl or bsal showed an independent evolution between mammals and fishes. Therefore, we inferred that the evolutionary selection of the main digestive lipase genes diverged into two types between mammals and fishes. These findings will provide valuable evidence for the study of lipid digestion in fish.

Dissecting the Interaction Deficiency of a Cartilaginous Fish Digestive Lipase with Pancreatic Colipase: Biochemical and Structural Insights

A full-length cDNA encoding digestive lipase (SmDL) was cloned from the pancreas of the smooth-hound (Mustelus mustelus). The obtained cDNA was 1350 bp long encoding 451 amino acids. The deduced amino acid sequence has high similarity with known pancreatic lipases. Catalytic triad and disulphide bond positions are also conserved. According to the established phylogeny, the SmDL was grouped with those of tuna and Sparidae lipases into one fish digestive lipase cluster. The recently purified enzyme shows no dependence for bile salts and colipase. For this, the residue-level interactions between lipase-colipase are yet to be clearly understood. The structural model of the SmDL was built, and several dissimilarities were noticed when analyzing the SmDL amino acids corresponding to those involved in HPL binding to colipase. Interestingly, the C-terminal domain of SmDL which holds the colipase shows a significant role for colipase interaction. This is apt to prevent the interaction between fish lipase and the pancreatic colipase which and can provide more explanation on the fact that the classical colipase is unable to activate the SmDL.