N-acylethanolamine acid amide hydrolase

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N-acylethanolamine acid amide hydrolase (NAAA) EC 3.5.1.- [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.

Contents

Mechanism

The overall enzyme mechanism involves cleavage into two chains, one of which contains the catalytic nucleophile, believed to be a cysteine residue. Unlike FAAH, which operates in basic conditions, this enzyme must operate under acidic conditions (pH ~4.5), and is completely inactivated at a pH of 8. Selective inhibitors of NAAA are ester and amide compounds, such as N-cyclohexanecarbonylpentadecylamine. NAAA is cleaved proteolytically at residue Cys-126. NAAA cleaves C-N non-peptide bonds in linear amides, particularly ethanolamides. Its mechanism is quite similar to that of AC, which is further supported by AC's ability to cleave N-acylethanolamines (NAEs), albeit at far lower rates and with different specificities. While mechanistic details are not very well known, catalytic activity of NAAA is thought to be activated by Cys-126 and Asp-145.

This is the speculated mechanism for the hydrolysis of ethanolamides by NAAA, which is very similar to that of acid ceramise. BreakdownofNAAA.jpg
This is the speculated mechanism for the hydrolysis of ethanolamides by NAAA, which is very similar to that of acid ceramise.

Structure

Currently, there is little information about NAAA's tertiary structure, due to its low homology to any of the other enzymes in the choloylglycine hydrolase family for which there is significant 3-dimensional structural information. In humans, this enzyme contains 359 residues. NAAA's primary structure is nearly identical to that of acid ceramidase (AC), whose only difference is the substitution of Leu at the 334th residue, for phenylalanine. The enzyme must be N-glycosylated at six sites in order for the enzyme to operate at its maximum activity level, all of which have the peptide sequence, Asn-Xxx-Ser/Thr. Unlike AC, NAAA does not form a heterodimer through disulfide bonds, but rather remains active as two separate cleaved peptides following hydrolysis.

Biological function

Fatty acid ethanolamines (FAEs) perform several physiological functions, most notably serving as messengers for pain and inflammation. NAAA's are found primarily in the lysosomal compartment of macrophages, in line with most inflammation-related proteins. The gene that codes for the protein is 4q21.1. There, they perform FAE hydrolysis, the final step in the signaling cascade for pain and inflammation, yielding an ethanolamine and a fatty acid. While it processes the cleavage of many different substrates, NAAA is most active with the substrate N-palmitoylethanolamine, suggesting that this is one of the key messengers of pain. NAAA activity in rats is highest in the lungs, while in humans it is highest in the liver, so there is cross-species variability in the enzyme's selective activity.

Disease relevance

Recent studies suggest that NAAA has significance in two widespread human conditions: chronic pain and obesity. Current research focuses on inhibiting the NAAA hydrolytic active site in order to control inflammation. It is still ambiguous as to whether reduced inflammation is correlated to reduced pain. ARN077, a β-lactone, has been one of the most intensely tested NAAA inhibitors, with the strongest promise of inhibition, as it blocks the catalytic cysteine via a thioester bond. The lack of homology between NAAA and FAAH makes NAAA-specific targeting drugs far more feasible. However, because the fatty acid concentration circulating throughout one's bloodstream is positively correlated with obesity, decreased NAAA activity is thought to be correlated with obesity.

This mechanism shows the inhibition of the catalytic cysteine by the most-tested b-lactone, ARN077. AR007.jpg
This mechanism shows the inhibition of the catalytic cysteine by the most-tested β-lactone, ARN077.

Industrial relevance

While no drugs targeting NAAA have entered the market yet, there is currently substantial research being done on the activation, and specific targeting and inhibition of NAAA. Activation of NAAA is spurred by the addition of phospholipids, and targeted inhibition by different buffers. Findings in these areas may be able to develop drugs to combat chronic pain and obesity.

Evolution

While NAAA operates much like fatty acid amide hydrolase (HUGO gene symbol: FAAH), the two enzymes are not homologous.

On the other hand, NAAA is homologous to acid ceramidase (HUGO gene symbol: ASAH1), sharing 30% sequence identity at the amino acid level in humans ENSEMBL.

Historical significance

NAAA was discovered in 2007 as an alternative source of anandamide hydrolysis. Previously, FAAH was the only known enzyme to be responsible for the degradation of these endocannabinoids, functioning in a pH range of 8.5-10. NAAA's discovery served as an explanation for endocannabinoids and anti-inflammatory ethanolamines in acidic environments, as its peak functionality is found at a pH ~4.5-5. Because of its functional role similar to FAAH, it offers another option for drug development.

See also

Related Research Articles

Anandamide Chemical compound (fatty acid neurotransmitter)

Anandamide (ANA), also known as N-arachidonoylethanolamine (AEA), is a fatty acid neurotransmitter. Anandamide was the first endocannabinoid to be discovered: it participates in the body's endocannabinoid system by binding to cannabinoid receptors, the same receptors that the psychoactive compound THC in cannabis acts on. Anandamide is found in nearly all tissues in a wide range of animals. Anandamide has also been found in plants, including small amounts in chocolate. The name 'anandamide' is taken from the Sanskrit word ananda, which means "joy, bliss, delight", and amide.

URB597 Chemical compound

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.

Monoacylglycerol lipase

Monoacylglycerol lipase, also known as MAG lipase, acylglycerol lipase, MAGL, MGL or MGLL is an enzyme that, in humans, is encoded by the MGLL gene. MAGL is a 33-kDa, membrane-associated member of the serine hydrolase superfamily and contains the classical GXSXG consensus sequence common to most serine hydrolases. The catalytic triad has been identified as Ser122, His269, and Asp239.

Fatty acid amide hydrolase

Fatty acid amide hydrolase or FAAH is a member of the serine hydrolase family of enzymes. It was first shown to break down anandamide in 1993. In humans, it is encoded by the gene FAAH.

AM404

AM404, also known as N-arachidonoylaminophenol, 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.

Methoxy arachidonyl fluorophosphonate Chemical compound

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.

Amidase

In enzymology, an amidase is an enzyme that catalyzes the hydrolysis of an amide:

ASAHL Protein-coding gene in the species Homo sapiens

N-acylethanolamine-hydrolyzing acid amidase is an enzyme that in humans is encoded by the NAAA gene.

N-Acylphosphatidylethanolamines (NAPEs) are hormones released by the small intestine into the bloodstream when it processes fat. NAPEs travel to the hypothalamus in the brain and suppress appetite. This mechanism could be relevant for treating obesity.

N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) is an enzyme that catalyzes the release of N-acylethanolamine (NAE) from N-acyl-phosphatidylethanolamine (NAPE). This is a major part of the process that converts ordinary lipids into chemical signals like anandamide and oleoylethanolamine. In humans, the NAPE-PLD protein is encoded by the NAPEPLD gene.

<i>N</i>-Acylethanolamine Class of chemical compounds

An N-acylethanolamine (NAE) is a type of fatty acid amide formed when one of several types of acyl group is linked to the nitrogen atom of ethanolamine. These amides conceptually can be formed from a fatty acid and ethanolamine with the release of a molecule of water, but the known biological synthesis uses a specific phospholipase D to cleave the phospholipid unit from N-acylphosphatidylethanolamines. Another route relies on the transesterification of acyl groups from phosphatidylcholine by an N-acyltransferase (NAT) activity. The suffixes -amine and -amide in these names each refer to the single nitrogen atom of ethanolamine that links the compound together: it is termed "amine" in ethanolamine because it is considered as a free terminal nitrogen in that subunit, while it is termed "amide" when it is considered in association with the adjacent carbonyl group of the acyl subunit. Names for these compounds may be encountered with either "amide" or "amine" varying by author.

Palmitoylethanolamide (PEA) is an endogenous fatty acid amide, belonging to the class of nuclear factor agonists. PEA has been studied in in vitro and in vivo systems using exogenously added or dosed compound; there is evidence that it binds to a nuclear receptor, through which it exerts a variety of biological effects, some related to chronic inflammation and pain.

JZL195 Chemical compound

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 Chemical compound

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.

PF-04457845 is a potent and exquisitely selective inhibitor of the enzyme fatty acid amide hydrolase (FAAH), with an IC50 of 7.2nM, and both analgesic and antiinflammatory effects in animal studies comparable to naproxen.

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.

<i>N</i>-Acylamides

N-acyl amides are a general class of endogenous fatty acid compounds characterized by a fatty acyl group linked to a primary amine metabolite by an amide bond. Broadly speaking, N-acyl amides fall into several categories: amino acid conjugates, neurotransmitter conjugates, ethanolamine conjugates, and taurine conjugates. N-acyl amides have pleiotropic signaling functions in physiology, including in cardiovascular function, metabolic homeostasis, memory, cognition, pain, motor control and others. Initial attention focused on N-acyl amides present in mammalian organisms, however recently lipid signaling systems consisting of N-acyl amides have also been found to be present in invertebrates, such as Drosophila melanogaster. N-acyl amides play important roles in many biochemical pathways involved in a variety of physiological and pathological processes, as well as the metabolic enzymes, transporters, and receptors that regulate their signaling.

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.

FAAH2 Protein-coding gene in the species Homo sapiens

Fatty acid amide hydrolase 2 or FAAH2 is a member of the serine hydrolase family of enzymes.

References

  1. Kazuhito Tsuboi, Naoko Takezaki & Natsuo Ueda (August 2007). "The N-acylethanolamine-hydrolyzing acid amidase (NAAA)". Chemistry & Biodiversity . 4 (8): 1914–1925. doi:10.1002/cbdv.200790159. PMID   17712833. S2CID   32163665.
  2. Yong-Xin Sun, Kazuhito Tsuboi, Li-Ying Zhao, Yasuo Okamoto, Didier M. Lambert & Natsuo Ueda (October 2005). "Involvement of N-acylethanolamine-hydrolyzing acid amidase in the degradation of anandamide and other N-acylethanolamines in macrophages". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids . 1736 (3): 211–220. CiteSeerX   10.1.1.321.2849 . doi:10.1016/j.bbalip.2005.08.010. PMID   16154384.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. Kazuhito Tsuboi, Yong-Xin Sun, Yasuo Okamoto, Nobukazu Araki, Takeharu Tonai & Natsuo Ueda (March 2005). "Molecular characterization of N-acylethanolamine-hydrolyzing acid amidase, a novel member of the choloylglycine hydrolase family with structural and functional similarity to acid ceramidase". The Journal of Biological Chemistry . 280 (12): 11082–11092. doi: 10.1074/jbc.M413473200 . PMID   15655246.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. Martin Kaczocha, Sherrye T. Glaser, Janiper Chae, Deborah A. Brown & Dale G. Deutsch (January 2010). "Lipid droplets are novel sites of N-acylethanolamine inactivation by fatty acid amide hydrolase-2". The Journal of Biological Chemistry . 285 (4): 2796–2806. doi: 10.1074/jbc.M109.058461 . PMC   2807334 . PMID   19926788.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. Valerio Chiurchiu, Luca Battistini & Mauro Maccarrone (January 2015). "Endocannabinoid signaling in innate and adaptive immunity". Immunology . 144 (3): 352–364. doi:10.1111/imm.12441. PMC   4557672 . PMID   25585882.
  6. Yi Zhang, Gabriele E. Sonnenberg, Tesfaye Mersha Baye, Jack Littrell, Jennifer Gunnell, Ann DeLaForest, Erin MacKinney, Cecilia J. Hillard, Ahmed H. Kissebah, Michael Olivier & Russell A. Wilke (December 2009). "Obesity-related dyslipidemia associated with FAAH, independent of insulin response, in multigenerational families of Northern European descent". Pharmacogenomics . 10 (12): 1929–1939. doi:10.2217/pgs.09.122. PMC   3003434 . PMID   19958092.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. Didier M. Lambert & Giulio G. Muccioli (November 2007). "Endocannabinoids and related N-acylethanolamines in the control of appetite and energy metabolism: emergence of new molecular players". Current Opinion in Clinical Nutrition and Metabolic Care . 10 (6): 735–744. doi:10.1097/MCO.0b013e3282f00061. PMID   18089956. S2CID   17639044.
  8. Oscar Sasso, Guillermo Moreno-Sanz, Cataldo Martucci, Natalia Realini, Mauro Dionisi, Luisa Mengatto, Andrea Duranti, Glauco Tarozzo, Giorgio Tarzia, Marco Mor, Rosalia Bertorelli, Angelo Reggiani & Daniele Piomelli (March 2013). "Antinociceptive effects of the N-acylethanolamine acid amidase inhibitor ARN077 in rodent pain models". Pain . 154 (3): 350–360. doi:10.1016/j.pain.2012.10.018. PMC   3723234 . PMID   23218523.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. Jay M. West, Nikolai Zvonok, Kyle M. Whitten, Jodianne T. Wood & Alexandros Makriyannis (February 2012). "Mass spectrometric characterization of human N-acylethanolamine-hydrolyzing acid amidase". Journal of Proteome Research . 11 (2): 972–981. doi:10.1021/pr200735a. PMC   3706083 . PMID   22040171.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. Janani Ravi, Amita Sneh, Konstantin Shilo, Mohd W. Nasser & Ramesh K. Ganju (May 2014). "FAAH inhibition enhances anandamide mediated anti-tumorigenic effects in non-small cell lung cancer by downregulating the EGF/EGFR pathway". Oncotarget . 5 (9): 2475–2486. doi:10.18632/oncotarget.1723. PMC   4058020 . PMID   24811863.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. Tatsuya Tai, Kazuhito Tsuboi, Toru Uyama, Kim Masuda, Benjamin F. Cravatt, Hitoshi Houchi & Natsuo Ueda (May 2012). "Endogenous molecules stimulating N-acylethanolamine-hydrolyzing acid amidase (NAAA)". ACS Chemical Neuroscience . 3 (5): 379–385. doi:10.1021/cn300007s. PMC   3382453 . PMID   22860206.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. Andrea Armirotti, Elisa Romeo, Stefano Ponzano, Luisa Mengatto, Mauro Dionisi, Claudia Karacsonyi, Fabio Bertozzi, Gianpiero Garau, Glauco Tarozzo, Angelo Reggiani, Tiziano Bandiera, Giorgio Tarzia, Marco Mor & Daniele Piomelli (May 2012). "beta-Lactones Inhibit N-acylethanolamine Acid Amidase by S-Acylation of the Catalytic N-Terminal Cysteine". ACS Medicinal Chemistry Letters . 3 (5): 422–426. doi:10.1021/ml300056y. PMC   4025845 . PMID   24900487.{{cite journal}}: CS1 maint: multiple names: authors list (link)

N-acylethanolamine acid amidase (gene name: NAAA ((ASAHL)) - Human Protein Atlas