85 kDa calcium-independent phospholipase A2 , also known as 85/88 kDa calcium-independent phospholipase A2, Group VI phospholipase A2, Intracellular membrane-associated calcium-independent phospholipase A2 beta, or Patatin-like phospholipase domain-containing protein 9 is an enzyme that in humans is encoded by the PLA2G6 gene. [5] [6] [7] [8] [9] [10]
The PLA2G6 gene is located on the p arm of chromosome 22 at position 13.1 and it spans 80,605 base pairs. [8] The PLA2G6 gene produces an 18.6 kDa protein composed of 166 amino acids. [11] [12] The resulting protein's structure has been shown to contain a lipase motif and 8 ankyrin repeats. [5] Different from rodent PLA2G6, which is known to share 90% overall amino acid sequence identity with that of the humans, the human PLA2G6 protein contains a 54-residue insertion which codes for a proline-rich region. This insertion has been shown to disrupt the last putative ankyrin repeat, as well as function as a linker region that segregates the N-terminal protein-binding domain from the C-terminal catalytic domain. [5] [13]
The PLA2G6 gene encodes for a phospholipase A2 enzyme, which is a subclass of enzyme that catalyzes the release of fatty acids from phospholipids. [8] This type of enzyme is responsible for breaking down (metabolizing) phospholipids. Phospholipid metabolism is essential for many body processes, including helping to maintain the integrity of the cell membrane.
Specifically, the A2 phospholipase produced from the PLA2G6 gene, sometimes called PLA2 group VI, helps to regulate the levels of a compound called phosphatidylcholine, which is abundant in the cell membrane. [14] The encoded protein may also play a role in phospholipid remodelling, arachidonic acid release, nitric oxide-induced or vasopressin-induced arachidonic acid release and in leukotriene and prostaglandin synthesis, Fas receptor-mediated apoptosis, and transmembrane ion flux in glucose-stimulated B-cells. [8] [9]
It addition, it has a role in cardiolipin (CL) deacylation, and is required for both speed and directionality of monocyte MCP1/CCL2-induced chemotaxis through regulation of F-actin polymerization at the pseudopods. Isoform ankyrin-iPLA2-1 and isoform ankyrin-iPLA2-2, which lack the catalytic domain, are probably involved in the negative regulation of PLA2G6 activity. [9] Several transcript variants encoding multiple isoforms have been described, but the full-length nature of only two of them have been determined to date. [8]
Phosphatidylcholine + H2O = 1-acylglycerophosphocholine + a carboxylate. [10] [9]
Mutations in PLA2G6 has been shown to result in mitochondrial deficiencies and associated disorders, including PLA2G6-associated neurodegeneration (PLAN), which has several subtypes and is also known as Neurodegeneration with brain iron accumulation type 2 (NBIA2), other forms of disease are also referred to as Parkinson disease 14 (PARK14), and hereditary spastic paraplegia. [15] [9] [10]
PLA2G6-associated neurodegeneration (PLAN) is a neurodegenerative disorder associated with iron accumulation in the brain, primarily in the basal ganglia. It is characterized by progressive extrapyramidal dysfunction leading to rigidity, dystonia, dysarthria and sensorimotor impairment. [9] [10] [16]
The most severe form is called infantile neuroaxonal dystrophy (INAD), also Neurodegeneration with brain iron accumulation type 2A (NBIA2A), and is characterized by pathologic axonal swelling and spheroid bodies in the central nervous system. Onset is within the first 2 years of life with death often by the age of 10 years. [9] [10] [16]
A later-childhood onset and more slowly progressive form is called atypical neuraxonal dystrophy (atypical NAD), also Neurodegeneration with brain iron accumulation type 2B (NBIA2B). [16]
An adult-onset disease called PLA2G6-related dystonia-parkinsonism develop dystonia and parkinsonism after earlier normal development, and is also caused by biallelic mutations to PLA2G6. [16]
Parkinson disease 14 (PARK14) is an adult-onset progressive neurodegenerative disorder characterized by parkinsonism, dystonia, severe cognitive decline, cerebral and cerebellar atrophy and absent iron in the basal ganglia on magnetic resonance imaging. [9] [10]
Hereditary spastic paraplegias are a diverse class of hereditary degenerative spinal cord disorders characterized by a slow, gradual, progressive weakness and spasticity (stiffness) of the legs. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. Rate of progression and the severity of symptoms are quite variable. [17]
Another disease associated with mutations in this gene is infantile neuroaxonal dystrophy.
PLA2G6 has been shown to have Protein-protein interactions with the following. [18] [9]
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. Acids trigger the release of bound calcium from cellular stores and the consequent increase in free cytosolic Ca2+, an essential step in calcium signaling to regulate intracellular processes. There are four major classes, termed A, B, C, and D, which are distinguished by the type of reaction which they catalyze:
Arachidonic acid is a polyunsaturated omega-6 fatty acid 20:4(ω-6), or 20:4(5,8,11,14). It is structurally related to the saturated arachidic acid found in cupuaçu butter. Its name derives from the Neo-Latin word arachis (peanut), but peanut oil does not contain any arachidonic acid.
The enzyme phospholipase A2 (EC 3.1.1.4, PLA2, systematic name phosphatidylcholine 2-acylhydrolase) catalyse the cleavage of fatty acids in position 2 of phospholipids, hydrolyzing the bond between the second fatty acid “tail” and the glycerol molecule:
Arachidonate 5-lipoxygenase, also known as ALOX5, 5-lipoxygenase, 5-LOX, or 5-LO, is a non-heme iron-containing enzyme that in humans is encoded by the ALOX5 gene. Arachidonate 5-lipoxygenase is a member of the lipoxygenase family of enzymes. It transforms essential fatty acids (EFA) substrates into leukotrienes as well as a wide range of other biologically active products. ALOX5 is a current target for pharmaceutical intervention in a number of diseases.
Infantile neuroaxonal dystrophy 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 about 6 and 18 months they begin to experience delays in acquiring new motor and intellectual skills, such as crawling or beginning to speak. Eventually they lose previously acquired skills.
Cyclooxygenase 1 (COX-1), also known as prostaglandin-endoperoxide synthase 1, is an enzyme that in humans is encoded by the PTGS1 gene. In humans it is one of two cyclooxygenases.
In enzymology, a ceramide kinase, also abbreviated as CERK, is an enzyme that catalyzes the chemical reaction:
Cytosolic phospholipase A2 is an enzyme that in humans is encoded by the PLA2G4A gene.
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 in eukaryotic cell physiology, in particular signal transduction pathways. Phospholipase C's role in signal transduction is its cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), which serve as second messengers. Activators of each PLC vary, but typically include heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca2+, and phospholipids.
Calcium-dependent phospholipase A2 is an enzyme that in humans is encoded by the PLA2G5 gene.
Peroxiredoxin-6 is a protein that in humans is encoded by the PRDX6 gene. It is a member of the peroxiredoxin family of antioxidant enzymes.
Cytosolic phospholipase A2 gamma is an enzyme that in humans is encoded by the PLA2G4C gene.
Group 10 secretory phospholipase A2 is an enzyme that in humans is encoded by the PLA2G10 gene.
Group XVI phospholipase A2 also commonly known as adipocyte phospholipase A2 (AdPLA) is an enzyme that in humans is encoded by the PLA2G16 gene. This enzyme has also been identified as PLA2G16, HRASLS3, HREV107, HREV107-3, MGC118754 or H-REV107-1 from studies on class II tumor suppression but not on its enzymatic properties. AdPLA is encoded by a 1.3 kilobase AdPLA messenger RNA and is an 18 kDa protein. It belongs to a superfamily of phospholipase A2 (PLA2) enzymes and is found primarily in adipose tissue. AdPLA regulates adipocyte lipolysis and release of fatty acids through a G-protein coupled pathway involving prostaglandin and EP3. It has also been reported to play a crucial role in the development of obesity in mouse models.
Patatin-like phospholipase domain-containing protein 3 (PNPLA3) also known as adiponutrin (ADPN), acylglycerol O-acyltransferase or calcium-independent phospholipase A2-epsilon (iPLA2-epsilon) is an enzyme that in humans is encoded by the PNPLA3 gene.
Lipoprotein-associated phospholipase A2 (Lp-PLA2) also known as platelet-activating factor acetylhydrolase (PAF-AH) is a phospholipase A2 enzyme that in humans is encoded by the PLA2G7 gene. Lp-PLA2 is a 45-kDa protein of 441 amino acids. It is one of several PAF acetylhydrolases.
CYP2U1 is a protein that in humans is encoded by the CYP2U1 gene
Neuropathy target esterase, also known as patatin-like phospholipase domain-containing protein 6 (PNPLA6), is an esterase enzyme that in humans is encoded by the PNPLA6 gene.
Arachidonyl trifluoromethyl ketone (ATK) is an analog of arachidonic acid. that inhibits some isoforms of the enzyme phospholipase A2. Specifically it inhibits the 85 kDa cystolic PLA2 (cPLA2).
Crotoxin (CTX) is the main toxic compound in the snake venom of the South American rattlesnake, Crotalus durissus terrificus. Crotoxin is a heterodimeric beta-neurotoxin, composed of an acidic, non-toxic and non-enzymatic subunit (CA), and a basic, weakly toxic, phospholipase A2 protein (CB). This neurotoxin causes paralysis by both pre- and postsynaptic blocking of acetylcholine signalling.
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This article incorporates text available under the CC BY 4.0 license. This article incorporates text from this source, which is in the public domain .
