Sandbox 47: Difference between revisions

Unlike many proteases, pancreatic lipase is secreted in its final form. However, it is only active in the presence of <scene name='Sandbox_47/Colipase/2'>colipase</scene>in the duodenum. Colipase is a 90-residue protein that forms a 1:1 <scene name='Sandbox_47/Colipasecontacts/2'>complex with lipase</scene>.<ref>Voet D, Voet JG, Pratt CW. "Fundamentals of Biochemistry: Life at the Molecular Level" John Wiley and Sons, Inc: New Jersey, 2008..</ref><ref>"van Tilbeurgh H, Sarda L, Verger R, Cambillau C. 1992. Structure of the pancreatic lipase-procolipase complex. Nature 359: 159-162. </ref> Colipase is also secreted in the pancreas, but in its inactive form, procolipase, which is activated by trypsin in the intestinal lumen. Colipase prevents the inhibitory effect of bile salts on the lipase-catalyzed intraduodenal hydrolysis of dietary long-chain triglycerides. Colipase binds to the C-terminal, non-catalytic domain of lipase, which stabilizes the active conformation and increases the hydrophobicity of the binding site.<ref>"Colipase". Wikipedia: The Free Encyclopedia. 5 July 2011 [http://en.wikipedia.org/wiki/Colipase]</ref> In other words, colipase activates the enzyme through the movement of the N-terminal domain loop or lid. Here, lipase and colipase can be seen <scene name='Sandbox_47/Lipasecolipasesubstrate/1'>in complex with a triacylglycerol</scene>.<ref>Hermoso J, Pignol D, Kerfelec B, Crenon I, Chapus C, Fontecilla-Camps JC. 1996. Lipase activation by nonionic detergents. J. Biol. Chem. 271: 18007-18016.</ref>