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Sandbox 47
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== '''Structure''' == | == '''Structure''' == | ||
| - | Horse pancreatic lipase (PDB ID 1hpl) consists of 449 amino acids and 705 well-defined water molecules in two subunits, <scene name='Sandbox_47/Lipasechaina/2'>A</scene> and <scene name='Sandbox_47/Lipasechainb/1'>B</scene>. The two chains interact through a variety of <scene name='Sandbox_47/Lipasecontacts/1'>contacts</scene>. Lipase also binds two <scene name='Sandbox_47/Lipase_calcium/2'>calcium ions</scene> as ligands through a variety of <scene name='Sandbox_47/Calciumcontacts/4'>contacts</scene>. Its <scene name='Sandbox_47/Lipasesecondarystructures/1'>secondary structure</scene> consists of 22% <scene name='Sandbox_47/Lipase_helix/2'>helices</scene> and 30% <scene name='Sandbox_47/Lipase_sheet/2'>beta sheets</scene>. It contains both <scene name='Sandbox_47/Lipase_hydrophobicres/2'>hydrophobic</scene> and <scene name='Sandbox_47/Lipase_polarres/1'>polar residues</scene>. The overall molecular structure of horse lipase has two well-defined domains. The N-terminal domain contains the <scene name='Sandbox_47/Activesite/3'>active site</scene> and has a typical alpha/beta hydrolase fold topology. The C-terminal domain, for colipase binding, has a beta-sheet sandwich topology.<ref>Bourne Y, Martinez C, Kerfelec B, Lombardo D, Chapus C, Cambillau C. 1994. Horse pancreatic lipase. J. mol Biol. 238: 709-732.</ref> | + | Horse pancreatic lipase (PDB ID 1hpl) consists of 449 amino acids and 705 well-defined water molecules in two subunits, <scene name='Sandbox_47/Lipasechaina/2'>A</scene> and <scene name='Sandbox_47/Lipasechainb/1'>B</scene>. The two chains interact through a variety of <scene name='Sandbox_47/Lipasecontacts/1'>contacts</scene>. Lipase also binds two <scene name='Sandbox_47/Lipase_calcium/2'>calcium ions</scene> as ligands through a variety of <scene name='Sandbox_47/Calciumcontacts/4'>contacts</scene>. Its <scene name='Sandbox_47/Lipasesecondarystructures/1'>secondary structure</scene> consists of 22% <scene name='Sandbox_47/Lipase_helix/2'>helices</scene> and 30% <scene name='Sandbox_47/Lipase_sheet/2'>beta sheets</scene>. It contains both <scene name='Sandbox_47/Lipase_hydrophobicres/2'>hydrophobic</scene> and <scene name='Sandbox_47/Lipase_polarres/1'>polar residues</scene>. The overall molecular structure of horse lipase has two well-defined domains. The N-terminal domain contains the <scene name='Sandbox_47/Activesite/3'>active site</scene> and has a typical alpha/beta hydrolase fold topology.The active site contains a catalytic triad that closely resembles that in serine proteases. The C-terminal domain, for colipase binding, has a beta-sheet sandwich topology.<ref>Bourne Y, Martinez C, Kerfelec B, Lombardo D, Chapus C, Cambillau C. 1994. Horse pancreatic lipase. J. mol Biol. 238: 709-732.</ref> |
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== '''Function''' == | == '''Function''' == | ||
| - | Most lipases act at a specific position on the glycerol backbone of the lipid substrate.<ref>"Lipase". Wikipedia: The Free Encyclopedia. 6 Nov 2011 [http://en.wikipedia.org/wiki/Lipase]</ref> Pancreatic lipase catalyzes the hydrolysis of triacylglycerols at their 1 and 3 positions to form 1,2-diacylglycerols and 2-acylglycerols together with the Na+ and | + | Most lipases act at a specific position on the glycerol backbone of the lipid substrate.<ref>"Lipase". Wikipedia: The Free Encyclopedia. 6 Nov 2011 [http://en.wikipedia.org/wiki/Lipase]</ref> Pancreatic lipase catalyzes the hydrolysis of triacylglycerols at their 1 and 3 positions to form 1,2-diacylglycerols and 2-acylglycerols together with the Na+ and K+ salts of fatty acids. The enzymatic activity of pancreatic lipase increases when it contacts the lipid-water interface. Binding to the lipid-water interface requries mixed micelles of phosphatidylcholine and bile acids as well as colipase. 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/1'>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.<ref>"Colipase". Wikipedia: The Free Encyclopedia. 5 July 2011 [http://en.wikipedia.org/wiki/Colipase]</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.<ref>"Colipase". Wikipedia: The Free Encyclopedia. 5 July 2011 [http://en.wikipedia.org/wiki/Colipase]</ref> | ||
Revision as of 20:24, 12 November 2011
| Please do NOT make changes to this Sandbox. Sandboxes 30-60 are reserved for use by Biochemistry 410 & 412 at Messiah College taught by Dr. Hannah Tims during Fall 2012 and Spring 2013. |
Lipase
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