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 . The N-terminal domain (red) is 337 residues long and consists mainly of 3 layer (alpha, beta, alpha) sandwich. The C-terminal domain (yellow) is 112 residues long and consists primarily of beta sandwich. Lipase also contains six . Disulfide bonds are indicated by the yellow rods and the Cys residues that they connect are shown in white. 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 pancreatic 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 (red) and basic (blue) residues is relatively even.
Catalytic Function
Pancreatic lipase contains three important that form the catalytic triad. They are highlighted in yellow. These three catalytic residues are all located in the 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.
