Drosophila melanogaster as a model system to study long-chain fatty acid amide metabolism

Insights into the differences related to the resistance mechanisms to the highly toxic fruit Hippomane mancinella (Malpighiales: Euphorbiaceae) between the larvae of the sister species Anastrepha acris and Anastrepha ludens (Diptera: Tephritidae) through comparative transcriptomics

The Manchineel, Hippomane mancinella ("Death Apple Tree") is one of the most toxic fruits worldwide and nevertheless is the host plant of the monophagous fruit fly species Anastrepha acris (Diptera: Tephritidae). Here we aimed at elucidating the detoxification mechanisms in larvae of A. acris reared on a diet enriched with the toxic fruit (6% lyophilizate) through comparative transcriptomics. We compared the performance of A. acris larvae with that of the sister species A. ludens, a highly polyphagous pest species that is unable to infest H. mancinella in nature. The transcriptional alterations in A. ludens were significantly greater than in A. acris. We mainly found two resistance mechanisms in both species: structural, activating cuticle protein biosynthesis (chitin-binding proteins likely reducing permeability to toxic compounds in the intestine), and metabolic, triggering biosynthesis of serine proteases and xenobiotic metabolism activation by glutathione-S-transferases and cytochrome P450 oxidoreductase. Some cuticle proteins and serine proteases were not orthologous between both species, suggesting that in A. acris, a structural resistance mechanism has been selected allowing specialization to the highly toxic host plant. Our results represent a nice example of how two phylogenetically close species diverged over recent evolutionary time related to resistance mechanisms to plant secondary metabolites.

ChIP-seq profiling of H3K4me3 and H3K27me3 in an invasive insect, Bactrocera dorsalis

Introduction: While it has been suggested that histone modifications can facilitate animal responses to rapidly changing environments, few studies have profiled whole-genome histone modification patterns in invasive species, leaving the regulatory landscape of histone modifications in invasive species unclear. Methods: Here, we screen genome-wide patterns of two important histone modifications, trimethylated Histone H3 Lysine 4 (H3K4me3) and trimethylated Histone H3 Lysine 27 (H3K27me3), in adult thorax muscles of a notorious invasive pest, the Oriental fruit fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), using Chromatin Immunoprecipitation with high-throughput sequencing (ChIP-seq). Results: We identified promoters featured by the occupancy of H3K4me3, H3K27me3 or bivalent histone modifications that were respectively annotated with unique genes key to muscle development and structure maintenance. In addition, we found H3K27me3 occupied the entire body of genes, where the average enrichment was almost constant. Transcriptomic analysis indicated that H3K4me3 is associated with active gene transcription, and H3K27me3 is mostly associated with transcriptional repression. Importantly, we identified genes and putative motifs modified by distinct histone modification patterns that may possibly regulate flight activity. Discussion: These findings provide the first evidence of histone modification signature in B. dorsalis, and will be useful for future studies of epigenetic signature in other invasive insect species.

The Biosynthesis and Metabolism of the N-Acylated Aromatic Amino Acids: N-Acylphenylalanine, N-Acyltyrosine, N-Acyltryptophan, and N-Acylhistidine

The fatty acid amides are a family of lipids composed of two chemical moieties, a fatty acid and a biogenic amine linked together in an amide bond. This lipid family is structurally related to the endocannabinoid anandamide (N-arachidonoylethanolamine) and, thus, is frequently referred to as a family of endocannabinoid-related lipids. The fatty acid amide family is divided into different classes based on the conjugate amine; anandamide being a member of the N-acylethanolamine class (NAE). Another class within the fatty acid amide family is the N-acyl amino acids (NA-AAs). The focus of this review is a sub-class of the NA-AAs, the N-acyl aromatic amino acids (NA-ArAAs). The NA-ArAAs are not broadly recognized, even by those interested in the endocannabinoids and endocannabinoid-related lipids. Herein, the NA-ArAAs that have been identified from a biological source will be highlighted and pathways for their biosynthesis, degradation, enzymatic modification, and transport will be presented. Also, information about the cellular functions of the NA-ArAAs will be placed in context with the data regarding the identification and metabolism of these N-acylated amino acids. A review of the current state-of-knowledge about the NA-ArAAs is to stimulate future research about this underappreciated sub-class of the fatty acid amide family.

The dietary arachidonic acid improved growth and immunity of honey bee (Apis mellifera ligustica)

Honeybees cannot synthesize arachidonic acid (ARA) themselves, only obtain it from food. Most pollen is deficient or contains a small amount of ARA. The necessity of supplementary ARA in bees' diet has not been studied. The objective of this study was to investigate the effects of dietary ARA levels on the growth and immunity of Apis mellifera ligustica. A total of 25 honeybee colonies were randomly assigned to five dietary groups which were fed basic diets supplemented with 0, 2, 4, 6, and 8% of ARA. The diet with 4% ARA improved the body weight of newly emerged worker bees compared with the control group. Supplement of ARA in honeybee diets changed the fatty acid composition of honeybee body. SFA and MUFA contents of bees' body declined, and PUFA content rised in the ARA group. Compared with the control group, the supplement of ARA in honeybee diets increased the contents of ARA, C22:6n-3 (DHA) and C18:3n-6 in bees' body significantly, but decreased the contents of C16:1 and C18:3n-3. The diet supplied with 4% ARA reduced the mortality rate of honeybee infected with Escherichia coli. The activity of immune enzymes (phenoloxidase, antitrypsin, and lysozyme) and the mRNA expression levels of immune genes (defensin-2, toll, myd88, and dorsal) were improved by ARA diets to varying degrees depending on the ARA levels, especially 4% ARA. These results suggested that dietary ARA could improve the growth, survival, and immune functions of honeybees. Supplement of ARA in bees' diet would be valuable for the fitness of honeybees.

Synthesis, Quantification, and Characterization of Fatty Acid Amides from In Vitro and In Vivo Sources

Fatty acid amides are a diverse family of underappreciated, biologically occurring lipids. Herein, the methods for the chemical synthesis and subsequent characterization of specific members of the fatty acid amide family are described. The synthetically prepared fatty acid amides and those obtained commercially are used as standards for the characterization and quantification of the fatty acid amides produced by biological systems, a fatty acid amidome. The fatty acid amidomes from mouse N₁₈TG₂ cells, sheep choroid plexus cells, Drosophila melanogaster, Bombyx mori, Apis mellifera, and Tribolium castaneum are presented.

Cannabinoids modulate food preference and consumption in Drosophila melanogaster

Cannabinoids have an important role in regulating feeding behaviors via cannabinoid receptors in mammals. Cannabinoids also exhibit potential therapeutic functions in Drosophila melanogaster, or fruit fly that lacks cannabinoid receptors. However, it remains unclear whether cannabinoids affect food consumption and metabolism in a cannabinoid receptors-independent manner in flies. In this study, we systematically investigated pharmacological functions of various cannabinoids in modulating food preference and consumption in flies. We show that flies display preferences for consuming cannabinoids, independent of two important sensory regulators Poxn and Orco. Interestingly, phyto- and endo- cannabinoids exhibit an inhibitory effect on food intake. Unexpectedly, the non-selective CB1 receptor antagonist AM251 attenuates the suppression of food intake by endocannabinoids. Moreover, the endocannabinoid anandamide (AEA) and its metabolite inhibit food intake and promote resistance to starvation, possibly through reduced lipid metabolism. Thus, this study has provided insights into a pharmacological role of cannabinoids in feeding behaviors using an adult Drosophila model.

Identification of catalytically distinct arylalkylamine N-acetyltransferase splicoforms from Tribolium castaneum

The assumption that structural or sequential homology between enzymes implies functional homology is a common misconception. Through in-depth structural and kinetic analysis, we are now beginning to understand the minute differences in primary structure that can alter the function of an enzyme completely. Alternative splicing is one method for which the activity of an enzyme can be controlled, simply by altering its length. Arylalkylamine N-acetyltransferase A (AANATA) in D. melanogaster, which catalyzes the N-acetylation of biogenic amines, has multiple splicoforms - alternatively spliced enzyme isoforms - with differing tissue distribution. As demonstrated here, AANAT1 from Tribolium castaneum is another such enzyme with multiple splicoforms. A screening assay was developed and utilized to determine that, despite only a 35 amino acid truncation, the shortened form of TcAANAT1 is a more active form of the enzyme. This implies regulation of enzyme metabolic activity via alternative splicing.

Anandamide Metabolites Protect against Seizures through the TRP Channel Water Witch in Drosophila melanogaster

Endocannabinoids protect against seizures, but their mechanism of action is still unclear, as they can have effects independent of known cannabinoid receptors. Using Drosophila melanogaster, which lacks canonical cannabinoid receptors, we report that the endocannabinoids anandamide and 2-arachidonoylglycerol protect against seizures in multiple fly seizure models. Surprisingly, inhibition of anandamide catabolism renders flies insensitive to protection by anandamide, indicating that anandamide metabolites are responsible for seizure protection. Consistent with this finding, arachidonic acid, a direct metabolite of anandamide, protects against seizures. To identify downstream effectors, we test for a role of transient receptor potential (TRP) channels and find that the TRPV1 antagonist capsazepine blocks the protective effect of anandamide. Also, a targeted genetic screen of TRP channels identifies water witch as a mediator of protection by anandamide. Using a Drosophila model, we reveal the role of arachidonic acid in seizure protection and identify a cannabinoid-receptor-1/2-independent mechanism of endocannabinoid seizure protection.

N-Acyl Amino Acids: Metabolism, Molecular Targets, and Role in Biological Processes

The lipid signal is becoming increasingly crowded as increasingly fatty acid amide derivatives are being identified and considered relevant therapeutic targets. The identification of N-arachidonoyl-ethanolamine as endogenous ligand of cannabinoid type-1 and type-2 receptors as well as the development of different–omics technologies have the merit to have led to the discovery of a huge number of naturally occurring N-acyl-amines. Among those mediators, N-acyl amino acids, chemically related to the endocannabinoids and belonging to the complex lipid signaling system now known as endocannabinoidome, have been rapidly growing for their therapeutic potential. Here, we review the current knowledge of the mechanisms for the biosynthesis and inactivation of the N-acyl amino acids, as well as the various molecular targets for some of the N-acyl amino acids described so far.

Knockdown of arylalkylamine N-acetyltransferase-like 2 in Drosophila melanogaster

Drosophila melanogaster produces fatty acid amides, and thus, provides a model to unravel the pathways for their biosynthesis. We previously demonstrated that arylalkylamine N-acetyltransferase-like 2 (AANATL2) from D. melanogaster will catalyze the formation of long-chain N-acylserotonins and N-acyldopamines in vitro. Generating silencing RNA via the UAS/GAL4 bipartite approach for targeted gene expression effectively decreased the endogenous levels of the AANATL2 transcripts in D. melanogaster, as shown by reverse transcription quantitative polymerase chain reaction. Consistent with these data, western blot analysis of the offspring of the AANATL2 knockdown flies using an anti-AANATL2 antibody revealed a significant reduction in the expression of the AANATL2 protein. Reduced expression of AANATL2 decreased the cellular levels of N-palmitoyldopamine (PALDA), providing strong evidence that AANATL2 is responsible for the biosynthesis of PALDA in vivo. This is the first time that the expression of an AANAT has been reduced in D. melanogaster to link one of these enzymes to the in vivo production of an N-acylarylalkylamide.

Bm-iAANAT3: Expression and characterization of a novel arylalkylamine N-acyltransferase from Bombyx mori

The arylalkylamine N-acyltransferases (AANATs) are enzymes that catalyze the acyl-CoA-dependent formation of N-acylarylalkylamides: acyl-CoA + arylalkylamine → N-acylarylalkylamides + CoA-SH. Herein, we describe our study of a previously uncharacterized AANAT from Bombyx mori: Bm-iAANAT3. Bm-iAANAT3 catalyzes the direct formation of N-acylarylalkylamides and accepts a broad range of short-chain acyl-CoA thioesters and amines as substrates. Acyl-CoA thioesters possessing an acyl chain length >10 carbon atoms are not substrates for Bm-iAANAT3. We report that Bm-iAANAT3 is a "versatile generalist", most likely, functioning in amine acetylation - a reaction in amine inactivation/excretion, cuticle sclerotization, and melanism. We propose a kinetic and chemical mechanism for Bm-iAANAT3 that is consistent with our steady-state kinetic analysis, dead-end inhibition studies, determination of the pH-rate profiles, and site-directed mutagenesis of a catalytically important amino acid in Bm-iAANAT3. These mechanistic studies of Bm-iAANAT3 will foster the development of novel compounds targeted against this enzyme and other insect AANATs for the control of insect pests.

Bm-iAANAT and its potential role in fatty acid amide biosynthesis in Bombyx mori

The purpose of this research is to unravel the substrate specificity and kinetic properties of an insect arylalkylamine N-acyltransferase from Bombyx mori (Bm-iAANAT) and to determine if this enzyme will catalyze the formation of long chain N-acylarylalkylamides in vitro. However, the determination of substrates and products for Bm-iAANAT in vitro is no guarantee that these same molecules are substrates and products for the enzyme in the organism. Therefore, RT-PCR was performed to detect the Bm-iAANAT transcripts and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) analysis was performed on purified lipid extracts from B. mori larvae (fourth instar, Bmi4) to determine if long chain fatty acid amides are produced in B. mori. Ultimately, we found that recombinant Bm-iAANAT will utilize long-chain acyl-CoA thioesters as substrates and identified Bm-iAANAT transcripts and long-chain fatty acid amides in Bmi4. Together, these data show Bm-iAANAT will catalyze the formation of long-chain N-acylarylalkylamides in vitro and provide evidence demonstrating that Bm-iAANAT has a role in fatty acid amide biosynthesis in B. mori, as well.

Insect Arylalkylamine N-Acyltransferases: Mechanism and Role in Fatty Acid Amide Biosynthesis

Arylalkylamine N-acyltransferases (AANATs) catalyze the formation of an N-acylamide from an acyl-CoA thioester and an amine. One well known example is the production of N-acetylserotonin from acetyl-CoA and serotonin, a reaction in the melatonin biosynthetic pathway from tryptophan. AANATs have been identified from a variety of vertebrates and invertebrates. Considerable efforts have been devoted to the mammalian AANAT because a cell-permeable inhibitor specifically targeted against this enzyme could prove useful to treat diseases related to dysfunction in melatonin production. Insects are an interesting model for the study of AANATs because more than one isoform is typically expressed by a specific insect and the different insect AANATs (iAANATs) serve different roles in the insect cell. In contrast, mammals express only one AANAT. The major role of iAANATs seem to be in the production of N-acetyldopamine, a reaction important in the tanning and sclerotization of the cuticle. Metabolites identified in insects including N-acetylserotonin and long-chain N-fatty acyl derivatives of dopamine, histidine, phenylalanine, serotonin, tyrosine, and tryptophan are likely produced by an iAANAT. In vitro studies of specific iAANATs are consistent with this hypothesis. In this review, we highlight the current metabolomic knowledge of the N-acylated aromatic amino acids and N-acylated derivatives of the aromatic amino acids, the current mechanistic understanding of the iAANATs, and explore the possibility that iAANATs serve as insect "rhymezymes" regulating photoperiodism and other rhythmic processes in insects.

N-FATTY ACYLGLYCINES: UNDERAPPRECIATED ENDOCANNABINOID-LIKE FATTY ACID AMIDES?

Long-chain N-fatty acylglycines, R-CO-NH-CH2-COOH (where "R" refers to an unsaturated or saturated alkyl chain of at least 14 carbons) are found in mammals and insects and are structurally related to the cell-signaling, lipid-like, N-fatty acylethanolamines, R-CO-NH-CH2-CH2-OH (where "R" refers to an alkyl chain of at least 14 carbons). Accumulating evidence demonstrates that the N-fatty acylglycines have important cellular functions, but much work remains in order to fully appreciate and understand these biomolecules including: (a) more work on their functions in vivo, (b) measuring their concentrations in the cell, (c) defining the pathways for the biosynthesis and degradation, and (d) understanding the metabolic interconversion(s) between the N-fatty acylglycines and other fatty acid amides. The purpose of reviewing the current state-of-knowledge about the N-fatty acylglycines is to stimulate future research about this intriguing family of biomolecules.

Structural and Mechanistic Analysis of Drosophila melanogaster Agmatine N-Acetyltransferase, an Enzyme that Catalyzes the Formation of N-Acetylagmatine

Agmatine N-acetyltransferase (AgmNAT) catalyzes the formation of N-acetylagmatine from acetyl-CoA and agmatine. Herein, we provide evidence that Drosophila melanogaster AgmNAT (CG15766) catalyzes the formation of N-acetylagmatine using an ordered sequential mechanism; acetyl-CoA binds prior to agmatine to generate an AgmNAT•acetyl-CoA•agmatine ternary complex prior to catalysis. Additionally, we solved a crystal structure for the apo form of AgmNAT with an atomic resolution of 2.3 Å, which points towards specific amino acids that may function in catalysis or active site formation. Using the crystal structure, primary sequence alignment, pH-activity profiles, and site-directed mutagenesis, we evaluated a series of active site amino acids in order to assign their functional roles in AgmNAT. More specifically, pH-activity profiles identified at least one catalytically important, ionizable group with an apparent pK_a of ~7.5, which corresponds to the general base in catalysis, Glu-34. Moreover, these data led to a proposed chemical mechanism, which is consistent with the structure and our biochemical analysis of AgmNAT.

GLYAT regulates JNK-mediated cell death in Drosophila

Cell death is a fundamental progress that regulates cell number, tissue homeostasis and organ size in development. The c-Jun N-terminal kinase (JNK) pathway has been evolutionarily conserved from fly to human, and plays essential roles in regulating cell death. To characterize additional genes that regulate JNK signaling, we performed a genetic screen in Drosophila and identified dGLYAT, a novel gene whose function was previously unknown, as a modulator of JNK-mediated cell death. We found that loss of dGLYAT suppressed JNK activation and cell death triggered by over-expression of Egr or Hep, or depletion of puc or lgl in development, suggesting dGLYAT regulates both ectopic and physiological functions of JNK pathway. Furthermore, we showed that loss of dGLYAT inhibits JNK-mediated ROS production, suggesting dGLYAT regulates multiple functions of JNK signaling in vivo.

2-pentadecyl-2-oxazoline: Identification in coffee, synthesis and activity in a rat model of carrageenan-induced hindpaw inflammation

N-acylethanolamines (NAEs) comprise a family of bioactive lipid molecules present in animal and plant tissues, with N-palmitoylethanolamine (PEA) having received much attention owing to its anti-inflammatory, analgesic and neuroprotective activities. 2-Pentadecyl-2-oxazoline (PEA-OXA), the oxazoline of PEA, reportedly modulates activity of N-acylethanolamine-hydrolyzing acid amidase (NAAA), which catabolizes PEA. Because PEA is produced on demand and exerts pleiotropic effects on non-neuronal cells implicated in neuroinflammation, modulating the specific amidases for NAEs (NAAA in particular) could be a way to preserve PEA role in maintaining cellular homeostasis through its rapid on-demand synthesis and equally rapid degradation. This study provides the first description of PEA-OXA in both green and roasted coffee beans and Moka infusions, and its synthesis. In an established model of carrageenan (CAR)-induced rat paw inflammation, PEA-OXA was orally active in limiting histological damage and thermal hyperalgesia 6h after CAR intraplantar injection in the right hindpaw and the accumulation of infiltrating inflammatory cells. PEA-OXA appeared to be more potent compared to ultramicronized PEA given orally at the same dose (10mg/kg). PEA-OXA markedly reduced also the increase in hindpaw myeloperoxidase activity, an index of polymorphonuclear cell accumulation in inflammatory tissues. NAAA modulators like PEA-OXA may serve to maximize availability of NAEs (e.g. PEA) while providing for recycling of the NAE components for further resynthesis.

Glycine N-acyltransferase-like 3 is responsible for long-chain N-acylglycine formation in N18TG2 cells

Long-chain fatty acid amides are signaling lipids found in mammals and other organisms; however, details of the metabolic pathways for the N-acylglycines and primary fatty acid amides (PFAMs) have remained elusive. Heavy-labeled precursor and subtraction lipidomic experiments in mouse neuroblastoma N18TG2 cells, a model cell line for the study of fatty acid amide metabolism, establish the biosynthetic pathways for the N-acylglycines and the PFAMs. We provide evidence that the N-acylglycines are formed by a long-chain specific glycine-conjugating enzyme, glycine N-acyltransferase-like 3 (GLYATL3). siRNA knockdown of GLYATL3 in the N18TG2 cells resulted in a decrease in the levels of the N-acylglycines and the PFAMs. This is the first report of an enzyme responsible for long-chain N-acylglycine production in cellula. The production of the PFAMs in N18TG2 cells was reported to occur by the oxidative cleavage of the N-acylglycines, as catalyzed by peptidylglycine α-amidating monooxygenase (PAM). siRNA knockdown of PAM resulted in an accumulation of [(13)C18]N-oleoylglycine and decreased levels of [(13)C18]oleamide when the N18TG2 cells were grown in the presence of [(13)C18]oleic acid. The addition of [1-(13)C]palmitate to the N18TG2 cell growth media led to the production of a family of [1-(13)C]palmitoylated fatty acid amides, consistent with the biosynthetic pathways detailed herein.

Omega-3 deficiency impairs honey bee learning

Deficiency in essential omega-3 polyunsaturated fatty acids (PUFAs), particularly the long-chain form of docosahexaenoic acid (DHA), has been linked to health problems in mammals, including many mental disorders and reduced cognitive performance. Insects have very low long-chain PUFA concentrations, and the effect of omega-3 deficiency on cognition in insects has not been studied. We show a low omega-6:3 ratio of pollen collected by honey bee colonies in heterogenous landscapes and in many hand-collected pollens that we analyzed. We identified Eucalyptus as an important bee-forage plant particularly poor in omega-3 and high in the omega-6:3 ratio. We tested the effect of dietary omega-3 deficiency on olfactory and tactile associative learning of the economically highly valued honey bee. Bees fed either of two omega-3-poor diets, or Eucalyptus pollen, showed greatly reduced learning abilities in conditioned proboscis-extension assays compared with those fed omega-3-rich diets, or omega-3-rich pollen mixture. The effect on performance was not due to reduced sucrose sensitivity. Omega-3 deficiency also led to smaller hypopharyngeal glands. Bee brains contained high omega-3 concentrations, which were only slightly affected by diet, suggesting additional peripheral effects on learning. The shift from a low to high omega-6:3 ratio in the Western human diet is deemed a primary cause of many diseases and reduced mental health. A similar shift seems to be occurring in bee forage, possibly an important factor in colony declines. Our study shows the detrimental effect on cognitive performance of omega-3 deficiency in a nonmammal.

Probing the chemical mechanism and critical regulatory amino acid residues of Drosophila melanogaster arylalkylamine N-acyltransferase like 2

Arylalkylamine N-acyltransferase like 2 (AANATL2) catalyzes the formation of N-acylarylalkylamides from the corresponding acyl-CoA and arylalkylamine. The N-acylation of biogenic amines in Drosophila melanogaster is a critical step for the inactivation of neurotransmitters, cuticle sclerotization, and melatonin biosynthesis. In addition, D. melanogaster has been used as a model system to evaluate the biosynthesis of fatty acid amides: a family of potent cell signaling lipids. We have previously showed that AANATL2 catalyzes the formation of N-acylarylakylamides, including long-chain N-acylserotonins and N-acyldopamines. Herein, we define the kinetic mechanism for AANATL2 as an ordered sequential mechanism with acetyl-CoA binding first followed by tyramine to generate the ternary complex prior to catalysis. Bell shaped kcat,app - acetyl-CoA and (kcat/Km)app - acetyl-CoA pH-rate profiles identified two apparent pKa,app values of ∼7.4 and ∼8.9 that are critical to catalysis, suggesting the AANATL2-catalyzed formation of N-acetyltyramine occurs through an acid/base chemical mechanism. Site-directed mutagenesis of a conserved glutamate that corresponds to the catalytic base for other D. melanogaster AANATL enzymes did not produce a substantial depression in the kcat,app value nor did it abolish the pKa,app value attributed to the general base in catalysis (pKa ∼7.4). These data suggest that AANATL2 catalyzes the formation of N-acylarylalkylamides using either different catalytic residues or a different chemical mechanism relative to other D. melanogaster AANATL enzymes. In addition, we constructed other site-directed mutants of AANATL2 to help define the role of targeted amino acids in substrate binding and/or enzyme catalysis.

Fatty acids, endocannabinoids and inflammation

From their phylogenetic and pharmacological classification it might be inferred that cannabinoid receptors and their endogenous ligands constitute a rather specialised and biologically distinct signalling system. However, the opposite is true and accumulating data underline how much the endocannabinoid system is intertwined with other lipid and non-lipid signalling systems. Endocannabinoids per se have many structural congeners, and these molecules exist in dynamic equilibria with different other lipid-derived mediators, including eicosanoids and prostamides. With multiple crossroads and shared targets, this creates a versatile system involved in fine-tuning different physiological and metabolic processes, including inflammation. A key feature of this 'expanded' endocannabinoid system, or 'endocannabinoidome', is its subtle orchestration based on interactions between a relatively small number of receptors and multiple ligands with different but partly overlapping activities. Following an update on the role of the 'endocannabinoidome' in inflammatory processes, this review continues with possible targets for intervention at the level of receptors or enzymes involved in formation or breakdown of endocannabinoids and their congeners. Although its pleiotropic character poses scientific challenges, the 'expanded' endocannabinoid system offers several opportunities for prevention and therapy of chronic diseases. In this respect, successes are more likely to come from 'multiple-target' than from 'single-target' strategies.

Mechanistic and Structural Analysis of a Drosophila melanogaster Enzyme, Arylalkylamine N-Acetyltransferase Like 7, an Enzyme That Catalyzes the Formation of N-Acetylarylalkylamides and N-Acetylhistamine

Arylalkylamine N-acetyltransferase like 7 (AANATL7) catalyzes the formation of N-acetylarylalkylamides and N-acetylhistamine from acetyl-CoA and the corresponding amine substrate. AANATL7 is a member of the GNAT superfamily of >10000 GCN5-related N-acetyltransferases, many members being linked to important roles in both human metabolism and disease. Drosophila melanogaster utilizes the N-acetylation of biogenic amines for the inactivation of neurotransmitters, the biosynthesis of melatonin, and the sclerotization of the cuticle. We have expressed and purified D. melanogaster AANATL7 in Escherichia coli and used the purified enzyme to define the substrate specificity for acyl-CoA and amine substrates. Information about the substrate specificity provides insight into the potential contribution made by AANATL7 to fatty acid amide biosynthesis because D. melanogaster has emerged as an important model system contributing to our understanding of fatty acid amide metabolism. Characterization of the kinetic mechanism of AANATL7 identified an ordered sequential mechanism, with acetyl-CoA binding first followed by histamine to generate an AANATL7·acetyl-CoA·histamine ternary complex prior to catalysis. Successive pH-activity profiling and site-directed mutagenesis experiments identified two ionizable groups: one with a pKa of 7.1 that is assigned to Glu-26 as a general base and a second pKa of 9.5 that is assigned to the protonation of the thiolate of the coenzyme A product. Using the data generated herein, we propose a chemical mechanism for AANATL7 and define functions for other important amino acid residues involved in substrate binding and regulation of catalysis.

Mechanistic and structural analysis of Drosophila melanogaster arylalkylamine N-acetyltransferases

Arylalkylamine N-acetyltransferase (AANAT) catalyzes the penultimate step in the biosynthesis of melatonin and other N-acetylarylalkylamides from the corresponding arylalkylamine and acetyl-CoA. The N-acetylation of arylalkylamines is a critical step in Drosophila melanogaster for the inactivation of the bioactive amines and the sclerotization of the cuticle. Two AANAT variants (AANATA and AANATB) have been identified in D. melanogaster, in which AANATA differs from AANATB by the truncation of 35 amino acids from the N-terminus. We have expressed and purified both D. melanogaster AANAT variants (AANATA and AANATB) in Escherichia coli and used the purified enzymes to demonstrate that this N-terminal truncation does not affect the activity of the enzyme. Subsequent characterization of the kinetic and chemical mechanism of AANATA identified an ordered sequential mechanism, with acetyl-CoA binding first, followed by tyramine. We used a combination of pH–activity profiling and site-directed mutagenesis to study prospective residues believed to function in AANATA catalysis. These data led to an assignment of Glu-47 as the general base in catalysis with an apparent pK_a of 7.0. Using the data generated for the kinetic mechanism, structure–function relationships, pH–rate profiles, and site-directed mutagenesis, we propose a chemical mechanism for AANATA.

Identification of an arylalkylamine N-acyltransferase from Drosophila melanogaster that catalyzes the formation of long-chain N-acylserotonins

Arylalkylamine N-acyltransferase-like 2(2) (AANATL2) from Drosophila melanogaster was expressed and shown to catalyze the formation of long-chain N-acylserotonins and N-acydopamines. Subsequent identification of endogenous amounts of N-acylserotonins and colocalization of these fatty acid amides and AANATL2 transcripts gives supporting evidence that AANATL2 has a role in the biosynthetic formation of these important cell signalling lipids.