A lipase is an enzyme that catalyzes the formation or cleavage (hydrolysis) of fats (lipids).[1] Lipases are a subclass of the esterases.
Lipases perform essential roles in the digestion, transport and processing of dietary lipids (e.g. triglycerides, fats, oils) in most, if not all, living organisms. Genes encoding lipases are even present in certain viruses.[2][3]
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Most lipases act at a specific position on the glycerol backbone of lipid substrate (A1, A2 or A3)(small intestine). For example, human pancreatic lipase (HPL),[4] which is the main enzyme that breaks down dietary fats in the human digestive system, converts triglyceride substrates found in ingested oils to monoglycerides and two fatty acids.
Several other types of lipase activities exist in nature, such as phospholipases[5] and sphingomyelinases,[6] however these are usually treated separately from "conventional" lipases.
Some lipases are expressed secreted by pathogenic organisms during the infection. In particular, Candida albicans has a large number of different lipases, possibly reflecting broad lipolytic activity, which may contribute to the persistence and virulence of C. albicans in human tissue.[7]
Although a diverse array of genetically distinct lipase enzymes are found in nature, and represent several types of protein folds and catalytic mechanisms, most are built on an alpha/beta hydrolase fold[4][8][9] (see image[10]) and employ a chymotrypsin-like hydrolysis mechanism involving a serine nucleophile, an acid residue (usually aspartic acid), and a histidine.[11][12]
Lipases are involved in diverse biological processes ranging from routine metabolism of dietary triglycerides to cell signaling[13] and inflammation.[14] Thus, some lipase activities are confined to specific compartments within cells while others work in extracellular spaces.
The main lipases of the human digestive system are human pancreatic lipase (HPL) and pancreatic lipase related protein 2 (PLRP2), which are secreted by the pancreas. Humans also have several other related enzymes, including hepatic lipase (HL), endothelial lipase, and lipoprotein lipase. Not all of these lipases function in the gut (see table).
| Name | Gene | Location | Description | Disorder |
| bile salt dependent lipase | ? | pancreas, breast milk | aids in the digestion of fats | |
| pancreatic lipase | PNLIP | digestive juice | In order to exhibit optimal enzyme activity in the gut lumen, HPL requires another protein, colipase, which is also secreted by the pancreas.[16] | |
| lysosomal lipase | LIPA | interior space of organelle: lysosome | Also referred to as lysosomal acid lipase (LAL or LIPA) or acid cholesteryl ester hydrolase | Cholesteryl ester storage disease (CESD) and Wolman disease are both caused by mutations in the gene encoding lysosomal lipase.[17] |
| hepatic lipase | LIPC | endothelium | Hepatic lipase acts on the remaining lipids carried on lipoproteins in the blood to regenerate LDL (low density lipoprotein). | - |
| lipoprotein lipase | LPL or "LIPD" | endothelium | Lipoprotein lipase functions in the blood to act on triacylglycerides carried on VLDL (very low density lipoprotein) so that cells can take up the freed fatty acids. | Lipoprotein lipase deficiency is caused by mutations in the gene encoding lipoprotein lipase.[18][19] |
| hormone-sensitive lipase | LIPE | intracellular | - | - |
| gastric lipase | LIPF | digestive juice | Functions in the infant at a near-neutral pH to aid in the digestion of lipids | - |
| endothelial lipase | LIPG | endothelium | - | - |
| pancreatic lipase related protein 2 | PNLIPRP2 or "PLRP2" - | digestive juice | - | - |
| pancreatic lipase related protein 1 | PNLIPRP1 or "PLRP1" | digestive juice | Pancreatic lipase related protein 1 is very similar to PLRP2 and HPL by amino acid sequence (all three genes probably arose via gene duplication of a single ancestral pancreatic lipase gene). However, PLRP1 is devoid of detectable lipase activity and its function remains unknown, even though it is conserved in other mammals.[20][21] | - |
| lingual lipase | ? | digestive juice | - | - |
Other lipases include LIPH, LIPI, LIPJ, LIPK, LIPM, LIPN, MGLL, DAGLA, DAGLB, and CEL.
There also are a diverse array of phospholipases, but these are not always classified with the other lipases.
Lipases serve important roles in human practices as ancient as yogurt and cheese fermentation. However, lipases are also being exploited as cheap and versatile catalysts to degrade lipids in more modern applications. For instance, a biotechnology company has brought recombinant lipase enzymes to market for use in applications such as baking, laundry detergents and even as biocatalysts[22] in alternative energy strategies to convert vegetable oil into fuel.[23][24]
Lipases are generally animal sourced, but can also be sourced microbially.
25. Gulzar, Bio-degradation of hydrocarbons using different bacterial and fungal species. Published in international conference on biotechnology and neurosciences. CUSAT (cochin university of science and technology), 2004
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