Sandbox 45

The two identical chains of lipase are pictured in blue-gray and green. Lipase has a consisting of 22% alpha helices, which are shown in blue, and 30% beta sheets, which are shown in bright green. The rest of the secondary structure consists of ordered, nonrepetitive structure. Lipase contains two domains. The N-terminal domain is 337 residues long and consists mainly of 3 layer (alpha, beta, alpha) sandwich. The C-terminal domain is 112 residues long and consists primarily of beta sandwich. Lipase also contains six which are illustrated by the yellow rods. These disulfide bonds occur between Cys 4 and Cys 10, Cys 90 and Cys 101, Cys 237 and Cys 261, Cys 285 and Cys 296, Cys 299 and Cys 304, and Cys 433 and Cys 449. Calcium ions, shown as bright green balls, are also seen interacting with the protein.

Hydrophobicity/Hydrophilicity

In lipase, there is a relatively equal distribution of and hydrophillc residues. Hydrophobic residues are shown in bright blue when clicking the green link. contribute to the relative hydophilicity of the protein since they can be protonated and deprotonated at varying pH levels, causing a charge to be present. The distribution and number of acidic and basic residues is relatively even.

Catalytic Function

Lipase contains three important which are highlighted in yellow. These three catalytic residues are all located in the A chain (N terminal domain) and consist of Ser 152, Asp 172, and His 263. Serine functions to form a covalent bond to the ester, forming a tetrahedral intermediate. Aspartate and histidine function in acid-base catalysis by accepting and donating hydrogen atoms to stabilize the reaction.

<Pancreatic lipase is shown here in a complex with the coenzyme colipase, which enhances lipase's function.  The two identical lipase chains are pictured in pink and blue.  The two identical chains of colipase are pictured in yellow and green.  Three ligands are shown in association with the two lipase chains.  Two calcium ions are shown in green as space-filling balls.  Beta-mercaptoethanol is also shown as yellow, grey, and red balls.  Lastly, (hydroxyethyloxy)tri(ethyloxy)octane is pictured as the larger grey, white, and red ball cluster directly in the middle of each of the lipase chains.