Properties and function of pancreatic lipase related protein 2.
The lipase gene family includes pancreatic triglyceride lipase and two pancreatic proteins, pancreatic lipase related proteins 1 and 2, with strong nucleotide and amino acid sequence homology to pancreatic triglyceride lipase. All three proteins have virtually identical three-dimensional structures. Of the pancreatic triglyceride lipase homologues, only pancreatic lipase related protein 2 has lipase activity. Like pancreatic triglyceride lipase, related protein 2 cleaves triglycerides, but it has broader substrate specificity. Pancreatic lipase related protein 2 also hydrolyzes phospholipids and galactolipids, two fats that are not substrates for pancreatic triglyceride lipase. The rat-related protein 2 also differs from pancreatic triglyceride lipase in sensitivity to bile salts and in response to colipase. Although the pancreas expresses both lipases, their temporal pattern of expression differs. Pancreatic lipase-related protein 2 mRNA appears before birth and persists into adulthood, whereas PTL mRNA first appears at the suckling-weanling transition. Additionally, intestinal enterocytes, paneth cells and cultured cytotoxic T-cells express mRNA encoding pancreatic lipase related protein 2. A physiological function for pancreatic lipase related protein 2 was demonstrated in mice that did not express this protein. Pancreatic lipase related protein 2 deficient mice malabsorbed fat in the suckling period, but not after weaning. They also had a defect in T-cell mediated cytotoxicity. Thus, pancreatic lipase related protein 2 is a lipase that participates in the cytotoxic activity of T-cells and plays a critical role in the digestion of breast milk fats.
Lowe
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ME
Washington University and St. Louis Children's Hospital, One Children's Place, St. Louis, MO 63141, USA. Lowe@pcfnotes1.wustl.edu
D000818:Animals; D006801:Humans; D007700:Kinetics; D008049:Lipase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation
D008049:Lipase; C075988:pancreatic lipase related protein 2