Submitted on August 29, 2002
Revised on September 24, 2002
Accepted on September 30, 2002
The triglyceride lipases of the pancreas
Mark E. Lowe
Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110
Corresponding Author: lowe{at}kids.wustl.edu
Pancreatic triglyceride lipase (PTL) and its protein cofactor, colipase, are required for efficient dietary triglyceride digestion. In addition to PTL, pancreatic acinar cells synthesize two pancreatic lipase related proteins (PLRP1 and PLRP2), which have a high degree of sequence and structural homology with PTL. PLRP1 has no known activity. PTL and PLRP2 differ in substrate specificity, behavior in bile salts and dependence on colipase. Each protein has a globular N-terminal domain, which contains the catalytic site for PTL and PLRP2, and a â-sandwich C-terminal domain, which includes the predominant colipase-binding site for PTL. Inactive and active conformations of PTL have been described. They differ in the position of a surface loop, the lid domain, and of the â5-loop. In the inactive conformation, the lid covers the active site and, upon activation by bile salt micelles and colipase or by lipid-water interfaces, the lid moves dramatically to open and configure the active site. After the lid movement, PTL and colipase create a large hydrophobic plateau that can interact with the lipid-water interface. A hydrophobic surface loop in the C-terminal domain, the â5’ loop, may also contribute to the interfacial-binding domain of the PTL-colipase complex.
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