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| Aliases | FAAH , fatty acid amide hydrolase, FAAH-1, PSAB | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 602935; MGI: 109609; HomoloGene: 68184; GeneCards: FAAH; OMA:FAAH - orthologs | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Fatty-acid amide hydrolase 1 (FAAH) [5] is a member of the serine hydrolase family of enzymes. It was first shown to break down anandamide (AEA), an N-acylethanolamine (NAE) in 1993. [6] In humans, it is encoded by the gene FAAH. [7] [8] [9]
FAAH is an integral membrane hydrolase with a single N-terminal transmembrane domain. In vitro, FAAH has esterase and amidase activity. [10] In vivo, FAAH is the principal catabolic enzyme for a class of bioactive lipids called the fatty acid amides (FAAs). Members of the FAAs include:
FAAH knockout mice display highly elevated (>15-fold) levels of N-acylethanolamines and N-acyltaurines in various tissues. Because of their significantly elevated anandamide levels, FAAH KOs have an analgesic phenotype, showing reduced pain sensation in the hot plate test, the formalin test, and the tail flick test. [16] Finally, because of their impaired ability to degrade anandamide, FAAH KOs also display supersensitivity to exogenous anandamide, a cannabinoid receptor (CB) agonist. [11]
Due to the ability of FAAH to regulate nociception, it is currently viewed as an attractive drug target for the treatment of pain. [17] [18] [19]
Studies in cells and animals and genetic studies in humans have shown that inhibiting FAAH may be a useful strategy to treat anxiety disorders, [20] [21] [22] as inhibition produce analgesic, anxiolytic, neuroprotective, and anti-inflammatory effects by elevated N-acylethanolamines (NAE's) and their activation of cannabinoid receptors. [23]
Activation of the cannabinoid receptor CB1 or CB2 in different tissues, including skin, inhibit FAAH, and thereby increases endocannabinoid levels. [24]
Based on the hydrolytic mechanism of fatty acid amide hydrolase, a large number of irreversible and reversible inhibitors of this enzyme have been developed. [25] [26] [27] [28] [29] [30] [31] [32]
Some of the more significant compounds are listed below;
Structural and conformational properties that contribute to enzyme inhibition and substrate binding imply an extended bound conformation, and a role for the presence, position, and stereochemistry of a delta cis double bond. [48]
Insulin medication increases the production and activity of FAAH. [49]
| SNP: rs324420 | |
|---|---|
| Name(s) | C385A, c.385C>A, p.Pro129Thr |
| Gene | FAAH |
| Chromosome | 1 |
| Region | Exon |
| External databases | |
| Ensembl | Human SNPView |
| dbSNP | 324420 |
| HapMap | 324420 |
| SNPedia | 324420 |
The FAAH gene contains a single nucleotide polymorphism (SNP) called rs324420. The variant allele, C385A, is associated with a higher sensitivity of FAAH to proteolytic degradation and a shorter half-life compared to the standard C variant. As a result, carriers of the A variant has increased N-acylethanolamine (NAE) levels and anandamide (AEA) signaling at the cannabinoid receptors. The A variant may be responsible for lower levels of the FAAH protein seen in high-performing athletes, providing increased physical and mental fitness. [50] However, among elite Polish athletes, the A variant is under-represented regardless of metabolic characteristics of their sport disciplines; this seems to suggest an opposite role for the A variant. [51]
A 2017 study found a strong correlation between national percentage of very happy people (as measured by the World Values Survey) and the presence of the rs324420 C385A allele in citizens' genetic make-up. [52]
The C385A allele was initially provisionally linked to drug abuse and dependence but this was not borne out in subsequent studies. According to later studies, carriers of the A allele are more likely to try cannabis, but less likely to become dependent. [20] : § 5.6
FAAH-OUT is a pseudogene downstream of the FAAH coding region. It expresses a long non-coding RNA (lncRNA) that increases the expression of FAAH. [53] In 2019, a Scottish woman named Jo Cameron was found to have both a previously unreported microdeletion mutation in FAAH-OUT and a rs324420 C385A mutation. The result is extreme disruption of FAAH function leading to elevated anandamide levels. She was immune to anxiety, unable to experience fear, and insensitive to pain. The frequent burns and cuts suffered due to her hypoalgesia healed quicker than average with little or no scarring. [54] [55] [56] Her son, who shares the FAAH-OUT deletion but has no C385A mutation, has a lesser degree of pain insensitivity. [54]
A 2023 study looks further into the functions of FAAH-OUT using transcriptomic analyses of cell models, some created anew using CRISPR-Cas9, others obtained from the 2019 patient. The study confirms that FAAH-OUT increases the expression of FAAH, both via its lncRNA product and through an intronic enhancer called FAAH-AMP. Loss of FAAH-OUT also changes the expression of a wide network of genes beyond FAAH itself. For example, although the pain insensitivity is mostly due to loss of FAAH function (via increased endocannabinoid levels and reduced ACKR3 expression), lack of depression and anxiety is instead due to a non-canonical Wnt pathway upregulating BDNF. The increased wound healing is due to both pathways: loss of FAAH function increases N-acyltaurine levels; the non-canonical Wnt pathway is also beneficial to healing. [53]
The enzyme is typically assayed making use of a radiolabelled anandamide substrate, which generates free labelled ethanolamine, although alternative LC-MS methods have also been described. [57] [58]
The first crystal structure of FAAH was published in 2002 (PDB code 1MT5). [9] Structures of FAAH with drug-like ligands were first reported in 2008, and include non-covalent inhibitor complexes and covalent adducts. [59]
The slime mold Dictyostelium discoideum produces a semispecific FAAH inhibitor. By controlling the levels of FAAH activity, they modulate endogenous N-acylethanolamine levels. [23]
In the Enzyme Commission numbering scheme, "fatty acid amide hydrolase" is EC 3.5.1.99. The number applies to all enzymes that have the chemical activity; in humans it covers both the genes FAAH and FAAH2 . The systematic name is "fatty acylamide amidohydrolase". Recorded synonyms include "oleamide hydrolase", "anandamide amidohydrolase". [60]
Anandamide (ANA), also referred to as N-arachidonoylethanolamine (AEA) is a fatty acid neurotransmitter belonging to the fatty acid derivative group known as N-Acylethanolamine (NAE). Anandamide takes its name from the Sanskrit word ananda, meaning "joy, bliss, delight," plus amide. Anandamide, the first discovered endocannabinoid, engages with the body's endocannabinoid system by binding to the same cannabinoid receptors that THC found in cannabis acts on. Anandamide can be found within tissues in a wide range of animals. It has also been found in plants, such as the cacao tree.
URB597 (KDS-4103) is a relatively selective and irreversible inhibitor of the enzyme fatty acid amide hydrolase (FAAH). FAAH is the primary degradatory enzyme for the endocannabinoid anandamide and, as such, inhibition of FAAH leads to an accumulation of anandamide in the CNS and periphery where it activates cannabinoid receptors. URB597 has been found to elevate anandamide levels and have activity against neuropathic pain in a mouse model.
The endocannabinoid system (ECS) is a biological system composed of endocannabinoids, which are endogenous lipid-based retrograde neurotransmitters that bind to cannabinoid receptors, and cannabinoid receptor proteins that are expressed throughout the vertebrate central nervous system and peripheral nervous system. The endocannabinoid system remains under preliminary research, but may be involved in regulating physiological and cognitive processes, including fertility, pregnancy, pre- and postnatal development, various activity of immune system, appetite, pain-sensation, mood, and memory, and in mediating the pharmacological effects of cannabis. The ECS plays an important role in multiple aspects of neural functions, including the control of movement and motor coordination, learning and memory, emotion and motivation, addictive-like behavior and pain modulation, among others.
2-Arachidonoylglycerol (2-AG) is an endocannabinoid, an endogenous agonist of the CB1 receptor and the primary endogenous ligand for the CB2 receptor. It is an ester formed from the omega-6 fatty acid arachidonic acid and glycerol. It is present at relatively high levels in the central nervous system, with cannabinoid neuromodulatory effects. It has been found in maternal bovine and human milk. The chemical was first described in 1994–1995, although it had been discovered some time before that. The activities of phospholipase C (PLC) and diacylglycerol lipase (DAGL) mediate its formation. 2-AG is synthesized from arachidonic acid-containing diacylglycerol (DAG).
AM404, also known as N-arachidonoylphenolamine, is an active metabolite of paracetamol (acetaminophen), responsible for all or part of its analgesic action and anticonvulsant effects. Chemically, it is the amide formed from 4-aminophenol and arachidonic acid.
Oleamide is an organic compound with the formula CH3(CH2)7CH=CH(CH2)7CONH2. It is the amide derived from the fatty acid oleic acid. It is a colorless waxy solid and occurs in nature. Sometimes labeled as a fatty acid primary amide (FAPA), it is biosynthesized from N-oleoylglycine.
Methoxy arachidonyl fluorophosphonate, commonly referred as MAFP, is an irreversible active site-directed enzyme inhibitor that inhibits nearly all serine hydrolases and serine proteases. It inhibits phospholipase A2 and fatty acid amide hydrolase with special potency, displaying IC50 values in the low-nanomolar range. In addition, it binds to the CB1 receptor in rat brain membrane preparations (IC50 = 20 nM), but does not appear to agonize or antagonize the receptor, though some related derivatives do show cannabinoid-like properties.
JZL184 is an irreversible inhibitor for monoacylglycerol lipase (MAGL), the primary enzyme responsible for degrading the endocannabinoid 2-arachidonoylglycerol (2-AG). It displays high selectivity for MAGL over other brain serine hydrolases, including the anandamide-degrading enzyme fatty acid amide hydrolase (FAAH), thereby making it a useful tool for studying the effects of endogenous 2-AG signaling, in vivo. Administration of JZL184 to mice was reported to cause dramatic elevation of brain 2-AG leading to several cannabinoid-related behavioral effects.
An N-acylethanolamine (NAE) is a type of fatty acid amide where one of several types of acyl groups is linked to the nitrogen atom of ethanolamine, and highly metabolic formed by intake of essential fatty acids through diet by 20:4, n-6 and 22:6, n-3 fatty acids, and when the body is physically and psychologically active,. The endocannabinoid signaling system (ECS) is the major pathway by which NAEs exerts its physiological effects in animal cells with similarities in plants, and the metabolism of NAEs is an integral part of the ECS, a very ancient signaling system, being clearly present from the divergence of the protostomian/deuterostomian, and even further back in time, to the very beginning of bacteria, the oldest organisms on Earth known to express phosphatidylethanolamine, the precursor to endocannabinoids, in their cytoplasmic membranes. Fatty acid metabolites with affinity for CB receptors are produced by cyanobacteria, which diverged from eukaryotes at least 2000 Million years ago (MYA), by brown algae which diverged about 1500 MYA, by sponges, which diverged from eumetazoans about 930 MYA, and a lineages that predate the evolution of CB receptors, as CB1 – CB2 duplication event may have occurred prior to the lophotrochozoan-deuterostome divergence 590 MYA. Fatty acid amide hydrolase (FAAH) evolved relatively recently, either after the evolution of fish 400 MYA, or after the appearance of mammals 300 MYA, but after the appearance of vertebrates. Linking FAAH, vanilloid receptors (VR1) and anandamide implies a coupling among the remaining ‘‘older’’ parts of the endocannabinoid system, monoglyceride lipase (MGL), CB receptors, that evolved prior to the metazoan–bilaterian divergence, but were secondarily lost in the Ecdysozoa, and 2-Arachidonoylglycerol (2-AG).
Palmitoylethanolamide (PEA) is an endogenous fatty acid amide, and lipid modulator.
JZL195 is a potent inhibitor of both fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), the primary enzymes responsible for degrading the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG), respectively.
LY-2183240 is a drug which acts both as a potent inhibitor of the reuptake of the endocannabinoid anandamide and as an inhibitor of fatty acid amide hydrolase (FAAH), the primary enzyme responsible for degrading anandamide. This leads to markedly elevated anandamide levels in the brain, and LY-2183240 has been shown to produce both analgesic and anxiolytic effects in animal models. While LY-2183240 is a potent inhibitor of FAAH, it has relatively poor selectivity and also inhibits several other enzyme side targets. Consequently, it was never developed for clinical use, though it remains widely used in research, and has also been sold as a designer drug.
N-Arachidonylglycine (NAGly) is a carboxylic metabolite of the endocannabinoid anandamide (AEA). Since it was first synthesized in 1996, NAGly has been a primary focus of the relatively contemporary field of lipidomics due to its wide range of signaling targets in the brain, the immune system and throughout various other bodily systems. In combination with 2‐arachidonoyl glycerol (2‐AG), NAGly has enabled the identification of a family of lipids often referred to as endocannabinoids. Recently, NAGly has been found to bind to G-protein coupled receptor 18 (GPR18), the putative abnormal cannabidiol receptor. NaGly is an endogenous inhibitor of fatty acid amide hydrolase (FAAH) and thereby increases the ethanolamide endocannabinoids AEA, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) levels. NaGly is found throughout the body and research on its explicit functions is ongoing.
IDFP is an organophosphorus compound related to the nerve agent sarin.
The endocannabinoid transporters (eCBTs) are transport proteins for the endocannabinoids. Most neurotransmitters are water-soluble and require transmembrane proteins to transport them across the cell membrane. The endocannabinoids on the other hand, are non-charged lipids that readily cross lipid membranes. However, since the endocannabinoids are water immiscible, protein transporters have been described that act as carriers to solubilize and transport the endocannabinoids through the aqueous cytoplasm. These include the heat shock proteins (Hsp70s) and fatty acid-binding proteins for anandamide (FABPs). FABPs such as FABP1, FABP3, FABP5, and FABP7 have been shown to bind endocannabinoids. FABP inhibitors attenuate the breakdown of anandamide by the enzyme fatty acid amide hydrolase (FAAH) in cell culture. One of these inhibitors (SB-FI-26), isolated from a virtual library of a million compounds, belongs to a class of compounds that act as an anti-nociceptive agent with mild anti-inflammatory activity in mice. These truxillic acids and their derivatives have been known to have anti-inflammatory and anti-nociceptive effects in mice and are active components of a Chinese herbal medicine used to treat rheumatism and pain in human. The blockade of anandamide transport may, at least in part, be the mechanism through which these compounds exert their anti-nociceptive effects.
N-acylethanolamine acid amide hydrolase (NAAA) EC 3.5.1.- is a member of the choloylglycine hydrolase family, a subset of the N-terminal nucleophile hydrolase superfamily. NAAA has a molecular weight of 31 kDa. The activation and inhibition of its catalytic site is of medical interest as a potential treatment for obesity and chronic pain. While it was discovered within the last decade, its structural similarity to the more familiar acid ceramidase (AC) and functional similarity to fatty acid amide hydrolase (FAAH) allow it to be studied extensively.
PF-3845 is a selective inhibitor of fatty acid amide hydrolase. It results in increased levels of anandamide and results in cannabinoid receptor-based effects. It has anti-inflammatory action in mice colitis models. Antidiarrheal and antinociceptive effects were also seen in mouse models of pain.
JNJ-42165279 is a drug developed by Janssen Pharmaceutica which acts as a potent and selective inhibitor of the enzyme fatty acid amide hydrolase (FAAH), with an IC50 of 70 nM. It is described as a covalently binding but slowly reversible selective inhibitor of FAAH. JNJ-42165279 is being developed for the treatment of anxiety disorders and major depressive disorder. Clinical development has progressed as far as Phase II human trials with two studies in patients with mood disorders registered in ClinicalTrials.gov.
An endocannabinoid enhancer (eCBE) is a type of cannabinoidergic drug that enhances the activity of the endocannabinoid system by increasing extracellular concentrations of endocannabinoids. Examples of different types of eCBEs include fatty acid amide hydrolase (FAAH) inhibitors, monoacylglycerol lipase (MAGL) inhibitors, and endocannabinoid transporter (eCBT) inhibitors. An example of an actual eCBE is AM404, the active metabolite of the analgesic paracetamol and a dual FAAH inhibitor and eCBRI.
Jo Cameron, also known as Patient PFS, is a Scottish woman who feels no pain and experiences little to no anxiety or other aspects of negative affect.
