Here, we describe probably the most representative NAAA inhibitors and briefly spotlight their pharmacological profile. allodynia caused by local swelling or nerve damage in animal models of pain and swelling. This finding stimulates further exploration of the pharmacology of NAAA inhibitors. strong class=”kwd-title” Keywords: N-acylethanolamine acid amidase, fatty acid ethanolamides, palmitoylethanolamide, pain, swelling, NAAA inhibitors 1. Intro The amides of long-chain fatty acids with ethanolamine, or fatty acid ethanolamides (FAEs), are a family of Rabbit polyclonal to AKT1 bioactive lipids that participate in the control of multiple physiological functions, including pain and inflammation.[1-4] Polyunsaturated FAEs such as arachidonoylethanolamide (anandamide, Fig. 1) are endogenous agonists for G protein-coupled cannabinoid receptors and participate in the control of stress-coping reactions and pain initiation.[1,5] On the other hand, monounsaturated and saturated FAEs, such as oleoylethanolamide (OEA, Fig. 1) and palmitoylethanolamide (PEA, Fig. 1), are potent or moderately potent agonists of the alpha-Amanitin peroxisome proliferator-activated alpha-Amanitin receptor- (PPAR-), a member of the nuclear receptor superfamily, which is responsible for most of their analgesic and anti-inflammatory properties. [4,6,7] Open in a separate windows Fig. 1 Chemical constructions of anandamide, oleoylethanolamide, and palmitoylethanolamide. FAEs are not stored in cells, but rather are produced on demand from cell membrane precursors. [8-10] OEA and PEA are generated in many mammalian cells, including neurons[11] and innate immune cells,[12] where a selective phospholipase, N-acylphosphatidylethanolamine phospholipase D (NAPE-PLD) releases them by cleaving their membrane precursor, em N /em -acylphosphatidylethanolamine.[13] The actions of these lipid messengers are terminated by enzyme-mediated hydrolysis, which is catalyzed by two known intracellular lipid amidases: N-acylethanolamine acid amidase (NAAA, previously referred to as N-acylethanolamine hydrolyzing acid amidase)[14-16] and fatty acid amide hydrolase (FAAH).[17,18] These enzymes share the ability to cleave lipid amide bonds, but differ in main structure, substrate selectivity, and cellular localization. NAAA is definitely a cysteine hydrolase that belongs to the em N /em -terminal nucleophile (Ntn) family of enzymes,[15,16,19] and bears a significant degree of sequence homology with the choloylglycine hydrolases, which share the ability to cleave non-peptide amide bonds.[20] NAAA displays a strong preference for saturated FAEs such as PEA,[15] while FAAH, a member of the amidase signature family of serine hydrolases, displays broader substrate selectivity, but hydrolyzes preferentially monounsaturated and polyunsaturated FAEs such as anandamide and OEA.[17] Moreover, NAAA seems to be mainly localized to the lysosomal compartment of macrophages,[21] whereas FAAH is alpha-Amanitin usually a membrane-bound enzyme that is found on the outer face of mitochondria and endoplasmic reticulum of most mammalian cells.[22] Like additional Ntn enzymes, such as acidity ceramidase, a lysosomal enzyme that hydrolyses ceramide to sphingosine and fatty acid,[23,24] NAAA alpha-Amanitin is activated by auto-proteolysis, which happens at acidic pH and generates a catalytically competent form of the enzyme.[25] Assessment of the primary structure of NAAA with those of the other members of the choloylglycine hydrolase family followed by site-directed mutagenesis experiments possess unequivocally identified cysteine 131 (Cys-131) in mice, or cysteine 126 (Cys-126) in humans, as the catalytic residue responsible for both auto-proteolysis and FAE hydrolysis.[26,27] The proposed mechanism of amide bond hydrolysis by Ntn enzymes consists in the attack of the catalytic N-terminal residue within the amide with formation of an acyl enzyme, followed by acyl enzyme hydrolysis with regeneration of the catalytically proficient enzyme.[28,29] According to this mechanism, the thiol group of the catalytic cysteine of NAAA would react with substrate with the formation of a thioester bond. Acylation of Cys-126 of human being NAAA by -lactones, a class of NAAA inhibitors, was recently shown by mass spectrometry.Replacement of the 3-phenylpropanamide in 11 having a linear alkyl chain as in compound 13 (Fig. exploration of the pharmacology of NAAA inhibitors. strong class=”kwd-title” Keywords: N-acylethanolamine acid amidase, fatty acid ethanolamides, palmitoylethanolamide, pain, swelling, NAAA inhibitors 1. Intro The amides of long-chain fatty acids with ethanolamine, or fatty acid ethanolamides (FAEs), are a family of bioactive lipids that participate in the control of multiple physiological functions, including pain and swelling.[1-4] Polyunsaturated FAEs such as arachidonoylethanolamide (anandamide, Fig. 1) are endogenous agonists for G protein-coupled cannabinoid receptors and participate in the control of stress-coping reactions and pain initiation.[1,5] On the other hand, monounsaturated and saturated FAEs, such as oleoylethanolamide (OEA, Fig. 1) and palmitoylethanolamide (PEA, Fig. 1), are potent or moderately potent agonists of the peroxisome proliferator-activated receptor- (PPAR-), a member of the nuclear receptor superfamily, which is responsible for most of their analgesic and anti-inflammatory properties. [4,6,7] Open in a separate windows Fig. 1 Chemical constructions of anandamide, oleoylethanolamide, and palmitoylethanolamide. FAEs are not stored in cells, but rather are produced on demand from cell membrane precursors.[8-10] OEA and PEA are generated in many mammalian tissues, including neurons[11] and innate immune cells,[12] where a selective phospholipase, N-acylphosphatidylethanolamine phospholipase D (NAPE-PLD) releases them by cleaving their membrane precursor, em N /em -acylphosphatidylethanolamine.[13] The actions of these lipid messengers are terminated by enzyme-mediated hydrolysis, which is catalyzed by two known intracellular lipid amidases: N-acylethanolamine acid amidase (NAAA, previously referred to as N-acylethanolamine hydrolyzing acid amidase)[14-16] and fatty acid amide hydrolase (FAAH).[17,18] These enzymes share the ability to cleave lipid amide bonds, but differ in main structure, substrate selectivity, and cellular localization. NAAA is definitely a cysteine hydrolase that belongs to the em N /em -terminal nucleophile (Ntn) family of enzymes,[15,16,19] and bears a significant degree of sequence homology with the choloylglycine hydrolases, which share the ability to cleave non-peptide amide bonds.[20] NAAA displays a strong preference for saturated FAEs such as PEA,[15] while FAAH, a member of the amidase signature family of serine hydrolases, displays broader substrate selectivity, but hydrolyzes preferentially monounsaturated and polyunsaturated FAEs such as anandamide and OEA.[17] Moreover, NAAA seems to be mainly localized to the lysosomal compartment of macrophages,[21] whereas FAAH is usually a membrane-bound enzyme that is found on the outer face of mitochondria and endoplasmic reticulum of most mammalian cells.[22] Like additional Ntn enzymes, such as acidity ceramidase, a lysosomal enzyme that hydrolyses ceramide to sphingosine and fatty acid,[23,24] NAAA is activated by auto-proteolysis, which happens at acidic pH and generates a catalytically competent form of the enzyme.[25] Assessment of the primary structure of NAAA with those of the other members of the choloylglycine hydrolase family followed by site-directed mutagenesis experiments possess unequivocally identified cysteine 131 (Cys-131) in mice, or cysteine 126 (Cys-126) in humans, as the catalytic residue responsible for both auto-proteolysis and FAE hydrolysis.[26,27] The proposed mechanism of amide bond hydrolysis by Ntn enzymes consists in the attack of the catalytic N-terminal residue within the amide with formation of an acyl enzyme, followed by acyl enzyme hydrolysis with regeneration of the catalytically proficient enzyme.[28,29] According to this mechanism, the thiol group of the catalytic cysteine of NAAA would react with substrate with the formation of a thioester bond. Acylation of Cys-126 of human being NAAA by -lactones, a class of NAAA inhibitors, was recently shown by mass spectrometry experiments.[30,31] The.