A phospholipase is an enzyme that hydrolyzes
phospholipid
Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
s into
fatty acid
In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...
s and other
lipophilic
Lipophilicity (from Greek language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are c ...
substances. There are four major classes, termed A, B, C, and D, which are distinguished by the type of reaction which they catalyze:
*Phospholipase A
**
Phospholipase A1 – cleaves the ''sn''-1
acyl chain (where ''sn'' refers to
stereospecific numbering
Glycerophospholipids or phosphoglycerides are glycerol-based phospholipids. They are the main component of biological membranes in eukaryotic cells. They are a type of lipid, of which its composition affects membrane structure and properties. Tw ...
).
**
Phospholipase A2 – cleaves the ''sn''-2
acyl chain, releasing
arachidonic acid
Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega−6 fatty acid 20:4(ω−6), or 20:4(5,8,11,14). It is a precursor in the formation of leukotrienes, prostaglandins, and thromboxanes.
Together with omega−3 fatty acids an ...
.
*
Phospholipase B – cleaves both ''sn''-1 and ''sn''-2
acyl chains; this enzyme is also known as a lysophospholipase.
*
Phospholipase C
Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role i ...
– cleaves before the phosphate, releasing
diacylglycerol and a phosphate-containing head group.
PLCs play a central role in
signal transduction
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a biochemical cascade, series of molecular events. Proteins responsible for detecting stimuli are generally termed receptor (biology), rece ...
, releasing the
second messenger
Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form of cell signaling, encompassing both first m ...
inositol triphosphate
Inositol trisphosphate or inositol 1,4,5-trisphosphate abbreviated InsP3 or Ins3P or IP3 is an inositol phosphate signaling molecule. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the p ...
.
*
Phospholipase D
Phospholipase D (PLD) (EC 3.1.4.4; also known as lipophosphodiesterase II, lecithinase D, choline phosphatase; systematic name: phosphatidylcholine phosphatidohydrolase) is an anesthetic-sensitive and mechanosensitive enzyme of the phospholipa ...
– cleaves after the phosphate, releasing
phosphatidic acid and an alcohol.
Types C and D are considered
phosphodiesterase
A phosphodiesterase (PDE) is an enzyme that breaks a phosphodiester bond. Usually, ''phosphodiesterase'' refers to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below. However, there are many oth ...
s.
Endothelial lipase is primarily a phospholipase.
Phospholipase A
2 acts on the intact lecithin molecule and hydrolyzes the fatty acid esterified to the second carbon atom. The resulting products are
lysolecithin and a fatty acid. Phospholipase A
2 is an enzyme present in the venom of
bees,
blennies and
viper snakes.
[D. M. Vasudevan & S. Sreekumari, ''Textbook of Biochemistry'' (5th ed.)]
See also
*
Patatin-like phospholipase
*
Infantile neuroaxonal dystrophy
Infantile neuroaxonal dystrophy (INAD) is a rare pervasive developmental disorder that primarily affects the nervous system. Individuals with infantile neuroaxonal dystrophy typically do not have any symptoms at birth, but between the ages of abo ...
References
Further reading
* Tappia, Paramjit S. & Dhalla, Naranjan S. (Editors): ''Phospholipases in Health and Disease.'' Springer, 2014.
rint Book
A book is a structured presentation of recorded information, primarily verbal and graphical, through a medium. Originally physical, electronic books and audiobooks are now existent. Physical books are objects that contain printed material, ...
External links
*
Peripheral membrane proteins
Cell signaling
Hydrolases
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