[Lipases of the digestive system]

Area of Science:

• Biochemistry
• Gastroenterology

Background:

• Gastrointestinal lipolysis is critical for fat digestion.
• Previous studies may have underestimated the role of gastric lipolysis.
• Recent in vitro data highlight the importance of gastric lipolysis.

Purpose of the Study:

• To review the role of gastric lipolysis in fat digestion.
• To investigate the characteristics of human gastric lipase activity.
• To understand the influence of amphiphiles and bile salts on lipolysis.

Main Methods:

• Screening of a rat tongue cDNA library using polyclonal antibodies against rat lingual lipase.
• Sequencing of the isolated cDNA clone to determine the amino acid sequence.
• Assessing human gastric lipase activity on tributyrin emulsion under varying conditions (amphiphiles, bile salts, surface tension).

Main Results:

• Rat lingual lipase cDNA was isolated and sequenced, showing limited homology with porcine pancreatic lipase.
• Human gastric lipase activity requires amphiphiles to prevent denaturation and is optimal between 8-13 dynes/cm surface tension.
• Amphiphiles decreasing surface tension below 8 dynes/cm irreversibly inhibit human gastric lipase.
• Human gastric lipase effectively hydrolyzes triacylglycerols in conditions mimicking the upper small intestine.

Conclusions:

• Human gastric lipase is enzymatically active in the presence of bile salts and alimentary proteins.
• Gastric lipolysis contributes significantly to lipid absorption, potentially explaining absorption in pancreatic lipase deficiency.