Phospholipases
Phospholipases are hydrolytic enzymes cleaving ester bonds in phospholipids. Based on According to the position of the cleaved ester bond we can differentiate between five types of phospholipases: : phospholipase A1, A2, B, C, D. Thanks to phospholipases, second messengers or arachidonic acid and subsequently eicosanoids can be formed.
Phospholipase A
Phospholipase A is an enzyme that hydrolytically cleaves phospholipids. Phospholipase A is divided into phospholipase A1 and phospholipase A2, they cleave different bonds in the phosholipid. Both are contained in lysosomes and in the digestive tract, where they have a digestive function.
Phospholipase A1
An enzyme that cleaves the acyl at position 1 in a phospholipid.
Phospholipase A2
It cleaves the acyl in position 2 from the phospholipid. Unsaturated fatty acids, such as arachidonic acid, are often found in this position. The release of arachidonate is an important step for some signaling pathways – both arachidonic acid itself and other substances derived from it (eicosanoids) have a signaling function. Enzymes with phospholipase 2 activity are also part of the venom of some snakes and spiders. The rest of the phospholipid that remains after sn-2 fatty acid cleavage (lysophospholipid) in the extracellular space has a haemolytic effect. After being bitten by some species of snakes and spiders, acute, even fatal, intravascular hemolysis can occur. In humans, extracellular phospholipase 2 is produced in pancreas as a proenzyme, it requires trypsin and Ca2+ ions for its activation.
Phospholipase B
It acts at the sites of action of phospholipase A1 and phospholipase A2. It hydrolyzes both ester bonds in position 1 and 2 of the respective phospholipid.
Phospholipase C
It hydrolyzes the ester bond in position 3 and releases diacylglycerol (DAG) and a phosphorylated base (e.g. phosphocholine). It is used in the signaling pathways of many cells of the human body, it hydrolyzes the phospholipid phosphatidylinositol-4,5-bisphosphate into two second messengers – diacylglycerol and inositol-1,4,5-trisphosphate.
For more information see wikiskripta:Buněčná signalizace(czech wikiskripta).Phospholipase D
It catalyzes the hydrolysis of phospholipids to release phosphatidic acid and compounds that were bound to phosphate (choline, serine, ethanolamine...). Phosphatidylcholine forms phosphatidic acid and choline is released.
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Related articles
Sources
- MATOUŠ, Bohuslav. Základy lékařské chemie a biochemie. 1. edition. Galén, 2010. ISBN 978-80-7262-702-8.
- BAYNES, John W – DOMINICZAK, Marek H. Medical biochemistry. 3. edition. Elsevier Mosby, 2009. ISBN 978-0-323-05371-6.
