Homo sapiens (human)
Fats constitute an important part of human nutrition. Fats can be made by the human body from carbohydrates, and this is why consuming too much carbohydrate can make you fat. They provide the construction material for the synthesis of compounds like cholesterol and the phospholipids of cell membranes. Fat molecules contain two types of building blocks: three fatty acids and one glycerol molecule. The fatty acids are connected to glycerol atoms to form triglycerides. Depending on the type of bonds in the hydrocarbon chain of the fatty acids there are saturated and unsaturated fatty acids. Fats are processed and broken up into more useful fragments by the action of proteins called lipases.
The structure here shows an example of such a lipase. It contains three sugar molecules on its surface, bound to asparagine sidechains. Lipases are located in the digestive tract. The most prominent example is the pancreatic lipase, but gastric lipase, in the stomach, is also important and seen here is its structure. It is particularly important for newborn babys, because their pancreatic lipase is underdeveloped. Lipase uses a mechanism for bond breaking that is similar to so-called serine proteases. The active site which helps break down the fat, contains a serine, a histidine and an asparagine residue, just like proteases. But the type of bond that is broken by this catalytic triad, is not an amide bond. The serine is hidden under a lid of residues that has to move to make the serine accessible to the substrate fat. The study of lipases is useful for the design of lipase inhibitors. Such inhibitors can reduce the amount of fat that is processed by the body. The unprocessed fats are then excreted and in this way one hopes to treat obesity caused by excessive fats. Other diseases like diabetes are also related.
Protein Data Bank (PDB)
author: Arno Paehler