Sequence of horse pancreatic lipase as determined by protein and cDNA sequencing. Implications for p-nitrophenyl acetate hydrolysis by pancreatic lipases.

The research article presents the complete sequence of horse pancreatic lipase, established through polypeptide chain and cDNA sequencing, and investigates its role in the hydrolysis of p-nitrophenyl acetate. Notably, a key residue present in other species is absent in horse lipases which brings forth questions regarding the mechanisms of pancreatic lipases.

Protein and cDNA Sequencing

• The study determined the complete sequence of the horse pancreatic lipase by combining polypeptide chain and complementary DNA (cDNA) sequencing.
• This technique allowed researchers to identify the order of amino acids in the lipase and the corresponding sequence in DNA.

Differences in Horse Pancreatic Lipase Structure

• In the molecular structure of the horse pancreatic lipase, the researchers noted that the Lys373 residue, which is present in human, porcine, and canine lipases, is not conserved.
• This is significant as the Lys373 residue is believed to be involved in p-nitrophenyl acetate hydrolysis, a chemical reaction of lipases.

Implications for Lipase Activity

• The study suggests that the hydrolysis of the p-nitrophenyl acetate by pancreatic lipases is the outcome of independent actions. These include a specific linear hydrolysis at the lipase’s active site, a quick acylation dependent on the presence of Lys373, and a non-specific hydrolysis possibly occurring in the enzyme’s C-terminal domain.
• The absence of Lys373 in horse pancreatic lipase, and the continued ability for hydrolysis, provides evidence that the pancreatic lipase only contains one active site. This raises questions regarding covalent catalysis by pancreatic lipases.

Proposed Binding Sites

• After comparing the sequences of horse, human, porcine, and canine pancreatic lipases, the research proposes three other residues (Lys349, Lys398, and Lys419) found in the C-terminal domain as possible candidates for lipase/colipase binding.
• This binding is important for lipase functioning and can provide valuable insights for scientific studies regarding pancreatic functions.