|Products||Glycerine / cholesterol + fatty acids|
Lipases are enzymes that split off free fatty acids from lipids such as glycerides or cholesterol esters ( lipolysis ). Physiologically, these enzymes play an important role by digesting fats and thus making the fat reserves stored in the body available. There are also a myriad of technological applications for these proteins.
In 1834, Johann Nepomuk Eberle recognized that pancreatic secretions can emulsify oils in water . Building on this knowledge, Claude Bernard found out in 1846 that an acidic reaction takes place during this process. The enzyme was initially called "Ferment émulsif", in 1896 Maurice Hanriot (1854–1933) then called it lipase. This later became the collective term for the entire group. Marcel von Nenecki (1847–1901) showed that the lipases of the pancreas must be activated by the bile.
Structure of true lipases EC 188.8.131.52
The esterases differ in their substrate spectrum. Accordingly, lipases prefer lipophilic , water-insoluble substrates. But they are also able to convert triglycerides from short-chain fatty acids , which are still water-soluble to a limited extent.
In contrast, the other esterases only hydrolyze short-chain, water-soluble substrates. In addition, the esterases differ from the lipases in their protein structures . Lipases have a lid ( engl. Lid ) over the active center, which is absent in esterases. The lipases are also found in all animals, plants and microorganisms as cellular or extracellular proteins. They belong to the family of serine hydrolases and have a reaction equilibrium for their specific reactions that depends on the water content of the overall system. Another important difference to esterases is that the hydrolysis of ester bonds of glycerol esters takes place at an oil-water interface .
Lipases often have no clear similarities in the amino acid sequence . When looking at the spatial structure, however, it becomes clear that lipases have common shapes. Accordingly, the lipases form a family of α / β hydrolase folds which is present in all lipases. It consists in the fact that in the center of the lipases eight almost parallel arranged β-sheets are placed, which in turn are enclosed by α-helices, with the exception of the second β-sheet, which is also arranged inversely in the structure.
With a few exceptions, the amino acids that are responsible for the catalytic action of the lipases are in the same positions. These amino acids form a catalytic triad , which is usually formed from the amino acids serine, histidine and aspartic acid. This triad is functionally, but not structurally, related to that of trypsin and subtilisin . In the amino acid sequence of α / β hydrolases, the amino acids appear in the following order: serine, aspartic acid, histidine. The serine is commonly found in the conserved pentapeptide of Gly-Xaa-Ser-Xaa-Gly.
- The lipoprotein lipase (LPL) is located on the extracellular membrane side of endothelial cells in various tissues (including adipose tissue ); it can break down the lipoprotein- bound fats in the blood and thus prepare them for cellular absorption. The hepatic triglyceride lipase is localized in the liver, for example.
- The pancreatic lipase (synonym: Steapsin ) is in the exocrine synthesized gland cells of the pancreas and passes through the pancreatic duct into the duodenum. There it splits the dietary fats into fatty acids, glycerine and mono- or diacylglycerine. These can then be absorbed into the enterocytes in the form of micelles with the help of bile salts . If the exocrine function of the pancreas is disturbed ( exocrine pancreatic insufficiency ), lipases in the form of pancreatins and / or rizoenzymes must be substituted, since incompletely digested fats are accompanied by painful gastrointestinal symptoms such as massive flatulence and steatorrhea .
- Another important type of lipase is the hormone-sensitive lipase . It splits the triglycerides stored in adipocytes and thus has a lipolytic effect.
- The gastric lipase is a lipase which is secreted by the gastric chief cells (chief cells) and is encoded by the LIPF gene.
Applications in industry and technology
Lipase is added to many detergents to increase cleaning performance.
Lipases are also used as biocatalysts in organic synthesis (e.g. for the production of sugar esters on an industrial scale ) and in the food industry for flavor production. They are also used in kinetic resolution .
Lipases can be isolated from a large number of different sources, with porcine pancreas lipase (PPL) or lipases from certain microorganisms being used for industrial purposes . Porcine pancreatic lipase is the most accurately described pancreatic lipase and consists of 449 amino acids with 7 disulfide bridges .
- Wolf-Dieter Müller-Jahncke , Christoph Friedrich , Ulrich Meyer: Medicinal history . 2nd, revised and expanded edition. Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart 2005, ISBN 978-3-8047-2113-5 , p. 115 .
- Hans Brockerhoff, Robert G. Jensen: Lipolytic enzymes. Academic Press, New York 1974, ISBN 0-12-134550-5 .
- Ulrike Schmid: Lipase-Catalyzed Synthesis of Structured Triglycerides. Process optimization and generation of selective lipase mutants by directed evolution. Dissertation, University of Stuttgart 2000. PDF .
- Katja Saulich: reaction kinetic experiments on lipase-catalyzed hydrolysis of rapeseed oil in water-in-oil emulsions. Dissertation, Brandenburg Technical University Cottbus 2008.
- D. Han, H. Rhee, S. Lee: Lipase reaction in aot-isooctane reversed micelles. Effect of water on equilibria. In: Biotechnology and Bioengineering , 30 : 381-388 (1987). PMID 18581372 .
- Andreas S. Bommarius, Bettina R. Riebel: Biocatalysis. Wiley-VCH, Weinheim 2004, ISBN 3-527-30344-8 .
- Joseph A. Schrag, Miroslaw Cygler: Lipases and α / β hydrolase fold. In: Methods in Enzymology , 284 : 85-107 (1997), PMID 9379946 . .
- Jean-Louis Arpigny, Karl E. Jaeger: Bacterial lipolytic enzymes. Classification and properties. In: Biochemical Journal , 343 : 177-183 (1999). PMID 10493927 ; PMC 1220539 (free full text).
- LIPF lipase, gastric, Homo sapiens (human)
|This text is based in whole or in part on the entry Lipase in the Flexikon , a Wiki of the DocCheck company . The takeover took place on July 10, 2004 under the then valid GNU license for free documentation .|