Lipase

Lipases are enzymes that of lipids such as glycerides, cholesterol esters or free fatty acids split off (lipolysis ). These enzymes play a physiologically important role in bring about the digestion of fat and make the data stored in the body fat reserves as available. There is also a myriad of technological applications for these proteins.

In a narrower sense lipase referred to in medical diagnosis, the pancreas- specific enteral lipase ( pancreatic lipase ).

Structure faithfully lipases EC 3.1.1.3

The esterases are distinguished by differences in the substrate spectrum. Thus, lipases prefer lipophilic, water-insoluble substrates. However, they are also able to convert triglycerides of short chain fatty acids, which are still limited in water.

In contrast, the other esterases hydrolyze only short-chain, water-soluble substrates.. In addition, the esterases from lipases differ in their protein structures. Lipases ( engl. lid ) a lid over the active site, which is absent in esterases. The lipases are also in all animals, plants and microorganisms present as cellular or extracellular proteins. They belong to the family of serine hydrolases and have for their specific reactions, a reaction equilibrium, which is the water content of the whole system depends. Another important difference is the esterases that the hydrolysis of ester bonds of glycerol esters occurring at an oil- water interface.

Lipases often have no clear similarities in the amino acid sequence. When viewing the three-dimensional structure, however, it is clear that lipases have common forms. Accordingly, the lipases are a family of α / β - hydrolase folds that is present in all the lipases. It is that almost eight β -strands arranged in parallel are placed in the center of the lipases, which are in turn surrounded by α -helices, with the exception of the second β -sheet, which is also inversely arranged in the structure.

With few exceptions, are the amino acids that are responsible for the catalytic activity of lipases at the same positions. These amino acids form a catalytic triad which is normally formed from the amino acids serine, histidine and aspartic acid. This triad is functionally, but not structurally related to the trypsin and subtilisin. In the amino acid sequence of α / β - hydrolase amino acids appear in the following order: serine, aspartic acid, histidine. The serine is commonly found in the conserved pentapeptide Gly -Xaa- Ser -Xaa -Gly.

Examples

Examples are:

• Lipoprotein lipase (LPL ) is located on the extracellular side of the membrane of endothelial cells in various tissues (including adipose tissue ); they can bound to lipoproteins in blood lipids split and prepare them for cellular uptake. Hepatic triglyceride lipase is localized, for example, in the liver.
• The pancreatic lipase ( synonym: steapsin ) is synthesized in the exocrine gland cells of the pancreas and passes through the pancreatic duct into the duodenum. There it splits the dietary fats into fatty acids, glycerol and mono- or diacylglycerols. These can then be added in the form of micelles with the aid of bile salts into the enterocytes. Only a small portion of the pancreatic lipase goes into the blood. There has a biological half-life of 7-14 hours.
• Another important Lipasenart is hormone -sensitive lipase. It splits the data stored in adipocytes triglycerides and thus acts lipolytically.
• The gastric lipase is a lipase, which is secreted by the gastric chief cells ( chief cells) and is encoded by the gene LIPF.

Applications in industry and technology

Lipases are used in the chemistry of fats for the production of soaps, fats with improved spreadability and for the production of cocoa butter equivalents.

Thank detergent is added to increase the cleaning power lipase.

In raw milk cheese they act aroma -forming. Butter is rancid faster. When pasteurizing the milk lipases are mostly destroyed.

Lipases are used as biocatalysts in organic synthesis (for example, for the production of sugar esters on an industrial scale ), and in the food industry to flavor production. Furthermore, they are used in the kinetic resolution.

Lipases can be isolated from a variety of sources, mostly for industrial purposes porcine (PPL ) or lipases are used by certain microorganisms. Porcine is the most accurately described pancreatic lipase and consists of 449 amino acids with seven disulfide bridges.