Phospholipase A2 Enzymes Research Articles

Beyond analgesia: repurposing NSAIDs as a novel strategy in antivenom therapy against Naja nigricollis envenomation

ObjectiveThis study aimed to explore the potential of repurposing non-steroidal anti-inflammatory drugs (NSAIDs) as antisnake venom agents using experimental and computational approaches.Data descriptionVirtual screening of 20 NSAIDs alongside Varespladib was conducted to obtain three top-scoring drugs (celecoxib, ketorolac, and ketoprofen); the antisnake venom efficacy of the three NSAIDs was evaluated using a combination of in vivo, ex vivo, in vitro and in silico approaches. In vivo and ex vivo experiments in mice, demonstrated that all three drugs exhibited significant (p < 0.05) antisnake venom activity against Naja nigricollis venom in a dose-dependent manner. Ketorolac provided complete protection with a 100% survival rate at doses of 100, 200, and 400 mg/kg, while celecoxib and ketoprofen showed survival rates ranging from 25 to 75%. The standard antivenom (ASV) also achieved a 100% survival rate at 0.6 mg/mL. Ex vivo results mirrored these findings, with ketorolac showing the highest survival rate (100%) and celecoxib exhibiting the lowest (50%). In vitro, the drugs demonstrated significant (p < 0.05) phospholipase A2 enzyme (PLA2) inhibition, with ketorolac achieving 96.65–99.86% inhibition at 1–0.0125 mg/mL. Molecular docking studies further supported these findings, revealing favorable binding affinities and interactions with key amino acid residues implicated in envenomation. In conclusion, these findings suggest that NSAIDs, particularly ketorolac, hold promise as potential antivenom therapies against Naja nigricollis envenomation, warranting further investigation in clinical studies.

Zahabba Patch: Innovation of Gingival Mucoadhesion Patch Combination of Ginger (Zingiber Officinale) and Black Cubit (Nigella Sativa) as Gingivitis Treatment

Background The prevalence of periodontal disease in Indonesia reaches 74.1%. Treatment of gingivitis by administering NSAIDs has a side effect of gastritis. Anti-inflammatory and analgesic derived from natural ingredients are known to cause minimal side effects on the patient's body. The active compounds gingerol in ginger (Zingiber officinale) and quercetin in black cumin (Nigella sativa) are known to function as good anti-inflammatory and analgesic agents. Objectives This study aims to analyze the effectiveness of gingerol in ginger extract and qurcetin in black cumin as an anti-inflammatory and analgesic packaged in a mucoadhesion patch as a treatment for gingivitis. Material and Methods Preparations of gingerol and quercetin were obtained by biocomputation using the PyRx program, the Pymol program, the RCSB PDB website, the Lipinski rule of five page, the PDBSum website, and also the pkCSM website. Physicochemical, pharmacokinetic, toxicity, and molecular docking tests were carried out to determine the biocompatibility of the active ingredients used. Results In the physicochemical tests, the compounds glycerol and quercetin can penetrate somatic cell membranes, have good solubility in water, can dissolve easily in the blood, are easily distributed in the body, and can maintain their position and bond strength with the target macro protein. The results of the AMES toxicity, Hepatotoxicity and skin sensitization tests showed negative values for both gingerol and quercetin. In the molecular docking test, the gingerol and quercetin compounds have a tendency to form bonds with COX-1 compared to arachidonic acid without having to increase the dose so that they become competitors to the native ligand. Conclusion The active compounds gingerol in ginger extract (Zingiber officinale) and quercetin in black cumin extract (Nigella sativa) contained in Zahabba patch are good anti-inflammatory and analgesic by inhibiting the synthesis of pro-inflammatory cytokines such as PGI2, PGE2, and TXA2 by being competitive inhibitor of the enzyme phospholipase A2 against membrane lipids and the enzyme cyclooxygenase-1 (COX-1) against arachidonic acid.

Elucidating on the Quaternary Structure of Viper Venom Phospholipase A2 Enzymes in Aqueous Solution.

This study focuses on the quaternary structure of the viper-secreted phospholipase A2 (PLA2), a central toxin in viper envenomation. PLA2 enzymes catalyse the hydrolysis of the sn-2 ester bond of membrane phospholipids. Small-molecule inhibitors that act as snakebite antidotes, such as varespladib, are currently in clinical trials. These inhibitors likely bind to the enzyme in the aqueous cytosol prior to membrane-binding. Thus, understanding its controversial solution structure is key for drug design. Crystal structures of PLA2 in the PDB show at least four different dimeric conformations, the most well-known being "extended" and "compact". This variability among enzymes with >50% sequence identity raises questions about their transferability to aqueous solution. Therefore, we performed extensive molecular dynamics (MD) simulations of several PLA2 enzymes in water to determine their quaternary structure under physiological conditions. The MD simulations strongly indicate that PLA2 enzymes adopt a "semi-compact" conformation in cytosol, a hybrid between extended and compact conformations. To our knowledge, this is the first study that determines the most favorable dimeric conformation of PLA2 enzymes in solution, providing a basis for advancements in snakebite envenoming treatment. Recognizing snakebite envenoming as a neglected tropical disease has driven the search for efficient, affordable alternatives to the current antivenoms. Therefore, understanding the main drug targets within snake venom is crucial to this achievement.

Contribution of individual phospholipase A2 enzymes to the cleavage of oxidized phospholipids in human blood plasma‡.

Phospholipids containing oxidized esterified PUFA residues (OxPLs) are increasingly recognized for multiple biological activities and causative involvement in disease pathogenesis. Pharmacokinetics of these compounds in blood plasma is essentially not studied. Human plasma contains both genuine phospholipases A2 (PAF-AH (also called Lp-PLA2) and sPLA2) and multifunctional enzymes capable of removing sn-2 residues in native and oxidized PLs (LCAT, PRDX6). The goal of this study was to compare relative activities of different PLA2 enzymes by analyzing cleavage of OxPAPC and OxPAPE by diluted plasma in the presence of enzyme inhibitors. We have found that human plasma demonstrated high total PLA2 activity against oxidized PCs and PEs. PAF-AH/Lp-PLA2 played a dominant role in LysoPC and LysoPE production as compared to other enzymes. Molecular species of OxPAPC and OxPAPE could be divided into 3 groups according to their degradation rate and sensitivity to PAF-AH/Lp-PLA2 inhibitor darapladib. Oxidatively truncated species were most rapidly metabolized in the presence of plasma; this process was strongly inhibited by darapladib. The rate of degradation of full-length OxPLs depended on the degree of oxygenation. Species containing 1 to 3 oxygen atoms were relatively stable to degradation in plasma, while OxPLs containing > 3 extra oxygens were degraded but at significantly slower rate than truncated species. In contrast to truncated species, degradation of full-length OxPLs with > 3 extra oxygens were only minimally inhibited by darapladib. These data provide further insights into the mechanisms regulating circulating levels of OxPLs and lipid mediators generated by PLA2 cleavage of OxPLs, namely oxylipins and LysoPC.

Secreted Phospholipases A2: Drivers of Inflammation and Cancer.

Secreted phospholipase 2 (sPLA2) is the largest family of phospholipase A2 (PLA2) enzymes with 11 mammalian isoforms. Each sPLA2 exhibits different localizations and specific properties, being involved in a very wide spectrum of biological processes. The enzymatic activity of sPLA2 has been well described; however, recent findings have shown that they could regulate different signaling pathways by acting directly as ligands. Arachidonic acid (AA) and its derivatives are produced by sPLA2 in collaboration with other molecules in the extracellular space, making important impacts on the cellular environment, being especially relevant in the contexts of immunity and cancer. For these reasons, this review focuses on sPLA2 functions in processes such as the promotion of EMT, angiogenesis, and immunomodulation in the context of tumor initiation and progression. Finally, we will also describe how this knowledge has been applied in the search for new sPLA2 inhibitory compounds that can be used for cancer treatment.

Venomous Peptides: Molecular Origin of the Toxicity of Snake Venom PLA2-like Peptides.

Snakebite envenoming claims 81-138 thousand lives annually, with vipers responsible for many of those. Phospholipase A2 (PLA2) enzymes and PLA2-like proteins are among the most important viper venom toxins. The latter are particularly intriguing, as three decades after their discovery, their molecular mechanism of toxicity is still poorly understood at best. PLA2-like proteins destabilize eukaryotic cell membranes through an unknown mechanism, causing an uncontrolled influx of Ca2+ ions and ultimately triggering cell death. It is now clear that the C-terminal segment is fundamental to the toxicity, as 13-mer peptides with the same sequence exhibit most or all of the activities of the complete PLA2-like proteins. To finally clarify the mechanism of toxicity of these venom peptides, we have simulated their interaction with model cell membranes. Molecular dynamics simulations showed that peptides initially dispersed across the cell membrane quickly and spontaneously migrated, aggregated, induced membrane thinning, and formed clear and transient membrane pores. We calculated the potentials of the mean force for Ca2+ transfer across the cell membranes through the transient pores. The pores significantly lower the free energy barrier for Ca2+ translocation, an effect that grows with the size of the peptide aggregates and, thus, with the pore radius. Ca2+ flowed across the membrane through the largest pores with almost no barrier. The permeability of Ca2+ through the largest pores exceeded the permeability of pharmaceutical drugs by 4 orders of magnitude, revealing the easiness by which Ca2+ overflows the intracellular medium. These results elucidate the illusive molecular origin of the toxicity of this famous class of snake venom-derived peptides.

The Inhibitory Potentials of the Root Extract and Fractions of Brenania brieyi (De Wild) (Rubiaceae) on Lactate Dehydrogenase, Phospholipase A2, and α- Amylase in Plasmodium falciparum - Infected Persons

Medicinal plants have been used as an alternative in malaria chemotherapy. This study aimed to determine the in vitro inhibitory potentials of the extract and fractions of Brenania brieyi on Lactate Dehydrogenase (LdH), Phospholipase A2 (PLA2), and α-Amylase enzyme extracted from Plasmodium falciparum. Cold maceration and Liquid-Liquid partitioning were used to obtain the extract and fractions respectively, using different solvent of varying polarity. Phytochemical analysis was done using Gas Chromatography-Flame Ionization detector (GCFID) method to identify and quantify different phytoconstituents. In vitro enzyme assay (α-Amylase, LdH and PLA2) were performed using standard procedure. The extract contained Alkaloids such as Spartein (5.05 µg/ml), Dihydrocytisine (23.12 µg/ml), Aphyllidine (5.25 µg/ml), Ribalinidine (2.65 µg/ml), Epihedrine (1.91 µg/ml), Saponins such as sapogenin (5.70 µg/ml), Tannins (16.25 µg/ml), Flavonoids such as Kaempferol (4.59 µg/ml), Catechin (5.50 µg/ml), Proanthocyanidin (9.81 µg/ml), Anthocyanin (3.22 µg/ml), Narigenin (3.62 µg/ml), Flavonones (8.73 µg/ml), Steroids (8.58 µg/ml), Polyphenols such as Reservatrol (20.68 µg/ml) and Glycosides such as cardiac glycoside (4.42 µg/ml), Cyanogenic glycosides (17.72 µg/ml) while Terpenoids are absent. The percentage inhibition of the enzyme (PLA2, LdH and α-amylase) at 100 mg/ml of extract showed the highest inhibition (37 %, 0 % and 38.33 %) when compared to controls, while ethyl acetate fraction has the highest inhibition (98 %, 34 % and 92 %) at P ˂ 0.05 at 100 mg/kg respectively. This study justifies the use of ethnomedicinal remedies (B. brieyi) in treating malaria in infected individuals. The study also suggests that the extract and fractions may act through the inhibition of plasmodial enzymes in infected persons.

Supramolecular Hybrids of Proteins from Habu Snake Venom with Discrete [Pt(CN)4]2- Complex.

The venom of the Habu snake Protobothrops flavoviridis (P. flavoviridis) is known to contain a diverse array of proteins and peptides, with a notable presence of phospholipase A2 (PLA2) enzymes. These PLA2 enzymes have been extensively studied for their function and molecular evolution. Nevertheless, several aspects, such as the physical properties and the self-assembly mechanism of hierarchical structure from the nanoscale to the microscale with different chemical compounds, remain poorly understood. This study aims to fill this knowledge gap by investigating the behavior of enzyme components purified from P. flavoviridis venom in the presence of anionic [Pt(CN)4]2- complexes, which have the potential for soft metallophilic interactions and interesting optical properties. The purified PLA2 isozymes were diluted in Dulbecco's phosphate buffered saline (D-PBS (-)) and combined with the anionic metal complex, resulting in the formation of microstructures several micrometers in size, which further grew to form fibrous structures. This novel approach of combining PLA2 enzymes with discrete functional metal complexes opens up exciting possibilities for designing flexible and functional supramolecular and biomolecular hybrid systems in aqueous environments. These findings shed light on the potential applications of snake venom enzymes in nanotechnology and bioengineering.

A novel phospholipase A2 is a core component of the typhoid toxin genetic islet

Salmonella Typhi, the cause of typhoid fever, is a bacterial pathogen of substantial global importance. Typhoid toxin is a secreted AB-type toxin that is a key S. Typhi virulence factor encoded within a 5-gene genetic islet. Four genes in this islet have well-defined roles in typhoid toxin biology; however, the function of the fifth gene is unknown. Here, we investigate the function of this gene, which we name ttaP. We show that ttaP is cotranscribed with the typhoid toxin subunit cdtB, and we perform genomic analyses that indicate that TtaP is very highly conserved in typhoid toxin islets found in diverse salmonellae. We show that TtaP is a distant homolog of group XIV secreted phospholipase A2 (PLA2) enzymes, and experimentally demonstrate that TtaP is a bona fide PLA2. Sequence and structural analyses indicate that TtaP differs substantially from characterized PLA2s, and thus represents a novel class of PLA2. Secretion assays revealed that TtaP is neither cosecreted with typhoid toxin, nor is it required for toxin secretion. Although TtaP is a phospholipase that remains associated with the S. Typhi cell, assays that probed for altered cell envelope integrity failed to identify any differences between WT S. Typhi and a ttaP deletion strain. Collectively, this study identifies a biochemical activity for the lone uncharacterized typhoid toxin islet gene and lays the groundwork for exploring how this gene factors into S. Typhi pathogenesis. This study further identifies a novel class of PLA2, enzymes that have a wide range of industrial applications.

Development and Optimization of a Bromothymol Blue-Based PLA2 Assay Involving POPC-Based Self-Assemblies.

Phospholipase A2 (PLA2) is a superfamily of phospholipase enzymes that dock at the water/oil interface of phospholipid assemblies, hydrolyzing the ester bond at the sn-2 position. The enzymatic activity of these enzymes differs based on the nature of the substrate, its supramolecular assemblies (micelle, liposomes), and their composition, reflecting the interfacial nature of the PLA2s and requiring assays able to directly quantify this interaction of the enzyme(s) with these supramolecular assemblies. We developed and optimized a simple, universal assay method employing the pH-sensitive indicator dye bromothymol blue (BTB), in which different POPC (3-palmitoyl-2-oleoyl-sn-glycero-1-phosphocholine) self-assemblies (liposomes or mixed micelles with Triton X-100 at different molar ratios) were used to assess the enzymatic activity. We used this assay to perform a comparative analysis of PLA2 kinetics on these supramolecular assemblies and to determine the kinetic parameters of PLA2 isozymes IB and IIA for each supramolecular POPC assembly. This assay is suitable for assessing the inhibition of PLA2s with great accuracy using UV-VIS spectrophotometry, being thus amenable for screening of PLA2 enzymes and their substrates and inhibitors in conditions very similar to physiologic ones.

ProcCluster® and procaine hydrochloride inhibit the replication of influenza A virus in vitro.

Treatment of influenza A virus infections is currently limited to few direct acting antiviral substances. Repurposing other established pharmaceuticals as antivirals could aid in improving treatment options. This study investigates the antiviral properties of ProcCluster® and procaine hydrochloride, two derivatives of the local anesthetic procaine, in influenza A virus infection of A549, Calu-3 and MDCK cells. Both substances inhibit replication in all three of these cell lines in multi-cycle experiments. However, cell line-dependent differences in the effects of the substances on viral RNA replication and subsequent protein synthesis, as well as release of progeny viruses in single-cycle experiments can be observed. Both ProcCluster® and procaine hydrochloride delay endosome fusion of the virus early in the replication cycle, possibly due to the alkaline nature of the active component procaine. In A549 and Calu-3 cells an additional effect of the substances can be observed at late stages in the first replication cycle. Interestingly, this effect is absent in MDCK cells. We demonstrate that ProcCluster® and procaine hydrochloride inhibit phospholipase A2 (PLA2) enzymes from A549 but not MDCK cells and confirm that specific inhibition of calcium independent PLA2 but not cytosolic PLA2 has antiviral effects. We show that ProcCluster® and procaine hydrochloride inhibit influenza A virus infection at several stages of the replication cycle and have potential as antiviral substances.

A study of the correlation between phospholipase A2 enzyme activity and anti-complement antibodies in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that affects multiple organs or organ systems. SLE and one of its most common complications, lupus nephritis (LN), are characterized by chronic inflammation due to the secretion of pro-inflammatory molecules and a tissue deposition of immune complexes formed by autoantibodies and their target antigens, such as double-stranded DNA, other nuclear antigens, and complement proteins. Increased activity of phospholipase A2 enzymes (PLA2) like calcium-independent PLA2 (iPLA2), secretory PLA2 (sPLA2), and cellular PLA2 (cPLA2) has a crucial role in the maintenance of the inflammatory process during the course of SLE. This study aimed to evaluate PLA2 activity and identify the dominant type of PLA2 enzymes in a cohort of Bulgarian patients with SLE and LN. Additionally, we investigated whether the increased PLA2 activity was correlated with the presence of autoantibodies specific to the complement proteins C3 and factor H.

Antinociceptive and Anti-Inflammatory Activities of Acetonic Extract from Bougainvillea x buttiana (var. Rose).

Background:Bougainvillea x buttiana is an ornamental plant with antioxidant, anti-inflammatory, and cytotoxic activities, which has been traditionally used to treat respiratory diseases. This study aimed to investigate whether the acetonic extract of Bougainvillea x buttiana var. Rose (BxbRAE-100%) has analgesic and anti-inflammatory properties and its potential action mechanisms. Methods: Analgesic and anti-inflammatory activities were evaluated using three murine pain models and two acute inflammation models. In vitro, the ability of the extract to inhibit proteolytic activity and the activities of the enzymes phospholipase A2 (PLA2) and cyclooxygenase (COX) were evaluated. In silico analysis was performed to predict the physicochemical and Absorption, distribution, metabolism, and excretion (ADME) profiles of the compounds previously identified in BxbRAE-100%. Results: In vivo BxbRAE-100% decreased the nociceptive behaviors in the writhing model, the tail immersion, and the formalin test, suggesting that the extract has the potential to relieve pain at peripheral and central levels. Additionally, topical or oral BxbRAE-100% treatment reduced dose-dependent 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced ear inflammation and carrageenan-induced paw edema, respectively. In vitro, BxbRAE-100% significantly inhibited proteolytic activity and PLA2, COX-1 and COX-2 activities. In silico, the compounds previously identified in BxbRAE-100% met Lipinski's rule of five and showed adequate ADME properties. Conclusions: These results support the use of B. x buttiana in Traditional Mexican Medicine and highlight its potential for the development of new treatments for pain and inflammation.

Biallelic null variants in PNPLA8 cause microcephaly by reducing the number of basal radial glia.

Patatin-like phospholipase domain-containing lipase 8 (PNPLA8), one of the calcium-independent phospholipase A2 enzymes, is involved in various physiological processes through the maintenance of membrane phospholipids. Biallelic variants in PNPLA8 have been associated with a range of paediatric neurodegenerative disorders. However, the phenotypic spectrum, genotype-phenotype correlations and the underlying mechanisms are poorly understood. Here, we newly identified 14 individuals from 12 unrelated families with biallelic ultra-rare variants in PNPLA8 presenting with a wide phenotypic spectrum of clinical features. Analysis of the clinical features of current and previously reported individuals (25 affected individuals across 20 families) showed that PNPLA8-related neurological diseases manifest as a continuum ranging from variable developmental and/or degenerative epileptic-dyskinetic encephalopathy to childhood-onset neurodegeneration. We found that complete loss of PNPLA8 was associated with the more profound end of the spectrum, with congenital microcephaly. Using cerebral organoids generated from human induced pluripotent stem cells, we found that loss of PNPLA8 led to developmental defects by reducing the number of basal radial glial cells and upper-layer neurons. Spatial transcriptomics revealed that loss of PNPLA8 altered the fate specification of apical radial glial cells, as reflected by the enrichment of gene sets related to the cell cycle, basal radial glial cells and neural differentiation. Neural progenitor cells lacking PNPLA8 showed a reduced amount of lysophosphatidic acid, lysophosphatidylethanolamine and phosphatidic acid. The reduced number of basal radial glial cells in patient-derived cerebral organoids was rescued, in part, by the addition of lysophosphatidic acid. Our data suggest that PNPLA8 is crucial to meet phospholipid synthetic needs and to produce abundant basal radial glial cells in human brain development.

Hepatotoxic Effects of an Oral Amiodarone in White Albino Rats: Sub-Acute Biochemical, and Histopathological Assessments

Amiodarone, potent antidysrhythmic, widely used drug that has been associated with hepatic toxicity in long-term or excessive use. In the presented study twelve rats were allocated into two groups and given daily doses via gastric gavage orally for two weeks as follows; The first group served as a control normal group, whereas the second got amiodarone at a dosage of 300mg/kg/day orally. Liver tissues were processed for light microscopy, and blood samples were examined for serum transaminases (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) and phospholipase a2 enzyme (Pla2) (which are thought to be an indicator of phospholipidosis and lipid buildup). Amiodarone was shown to produce hepatic histological abnormalities such as blood vessel congestion, leucocytic infiltration, liver degeneration, and stages of steatosis and necrosis of hepatocytes. The biochemical assessments were revealed that there was an elevation in amiodarone group's ALT and AST levels as a result of hepatic necrosis leading to leakage of enzymes content, while serum Pla2 was lowered significantly. Also, histopathology indicates stages of steatosis (Lipid accumulation) in hepatocytes, which may lead to farther damage in the late stages of hepatotoxicity.

Exploring the inhibitory potential of phytochemicals from Vernonia glaberrima leaves against snake venom toxins through computational simulation and experimental validation

Phospholipase A2 (PLA2) is an enzyme present in appreciable quantity in snake venoms which catalyze the hydrolysis of glycerophospholipids at sn-2 position and promote the release of lysophospholipids and fatty acids. 5-methylcoumarin-4-β-glucoside (5MC4BG) and lupeol were previously isolated from the leaves of V. glaberrima. The aim of this research was to evaluate effect of these compounds as potential inhibitors of snake venom toxins of Naja nigricollis using an in vitro and in silico studies. Antisnake venom studies was conducted using acidimetry while the molecular docking analysis against PLA2 enzyme from N. nigricollis was performed using Auto Dock Vina and ADME-Tox analysis was evaluated using swissADME and ProTox-II online servers. The two compounds (5MC4BG and Lupeol) were able to inhibit the hydrolytic actions of PLA2 enzyme with percentage inhibition ranging from 23.99 to 72.36 % and 21.97–24.82 % at 0.0625–1.00 mg/mL respectively while the standard ASV had 82.63 % at 1.00 mg/mL after 10 min incubation at 37 °C. Similar effects were observed after 30 min incubation, although there was significant increase in percentage inhibition of 5MC4BG and lupeol ranging from 66.51 to 83.73 % and 54.87–59.60 % at similar concentrations. Furthermore, the compounds were able to bind to the active site of PLA2 enzyme with high affinity (−7.7 to −6.3 kcal/mol); the standard ligand, Varespladib had a docking score of −6.9 kcal/mol and they exhibited favorable drug-likeness and pharmacokinetic properties and according to toxicity predictions, the two compounds are toxic. In conclusion, the leaf of V. glaberrima contains phytoconstituents with antisnake activity and thus, validates the hypothesis that, the phytoconstituents of V. glaberrima leaves has antisnake venom activity against N. nigricollis venom and thus, should be studied further for the development as antisnake venom agents.

The enzyme encoded by Myrmecia incisa, a green microalga, phospholipase A2 gene preferentially hydrolyzes arachidonic acid at the sn-2 position of phosphatidylcholine

The enzyme phospholipase A2 (PLA2) plays a crucial role in acyl remodeling of phospholipids via the Lands’ cycle, and consequently alters fatty acid compositions in triacylglycerol (TAG). In this study, a full-length cDNA sequence coding Myrmecia incisa phospholipase A2 (MiPLA2) was cloned using the technique of rapid amplification of cDNA ends. Comparison of the 1082-bp cDNA with its corresponding cloned DNA sequence revealed that MiPLA2 contained 3 introns. Mature MiPLA2 (mMiPLA2) had a conserved Ca2+-binding loop and a catalytic site motif that has been recognized in plant secretory PLA2 (sPLA2) proteins. Correspondingly, phylogenetic analysis illustrated that MiPLA2 was clustered within GroupXIA of plant sPLA2 proteins. To ascertain the function of MiPLA2, the cDNA coding for mMiPLA2 was subcloned into the vector pET-32a to facilitate the production of recombinant mMiPLA2 in Escherichia coli. Recombinant mMiPLA2 was purified and used for the in vitro enzyme reaction. Thin-layer chromatography profiles of the catalytic products generated by recombinant mMiPLA2 indicated a specificity for cleaving sn-2 acyl chains from phospholipids, thereby functionally characterizing MiPLA2. Although recombinant mMiPLA2 displayed a strong preference for phosphatidylethanolamine, it preferentially hydrolyzes arachidonic acid (ArA) at the sn-2 position of phosphatidylcholine. Results from the fused expression of p1300-sp-EGFP-mMiPLA2 illustrated that MiPLA2 was localized in the intercellular space of onion epidermis. Furthermore, the positive correlation between MiPLA2 transcription and free ArA levels were established. Consequently, the role of mMiPLA2 in the biosynthesis of ArA-rich TAG was elucidated. This study helps to understand how M. incisa preferentially uses ArA to synthesize TAG.

Copy number deletion of PLA2G4A affects the susceptibility and clinical phenotypes of schizophrenia

Phospholipase A2(PLA2) superfamily is recognized as being involved in the pathogenesis of schizophrenia by affecting lipid homeostasis in cell membranes. We hypothesized that PLA2 gene copy number variation (CNV) may affect PLA2 enzyme expression and be associated with schizophrenia risk. This study indicated that in the discovery stage, an increased copy number of PLA2G6 and the deletion of PLA2G3, PLA2G4A, PLA2G4F and PLA2G12F was associated with increased risk of schizophrenia. CNV segments involving six PLA2 genes were detected in publicly available datasets, including two deletion segments specific to the PLA2G4A gene. The relationship between the deletion of PLA2G4A and susceptibility to schizophrenia was then reaffirmed in the validation group of 806 individuals. There was a significant correlation between PLA2G4A deletion and the symptoms of poverty of thought in male patients and erotomanic delusion in females. Furthermore, ELISA results demonstrate a significant decrease in peripheral blood cytosolic PLA2(cPLA2) levels in patients with the PLA2G4A deletion genotype compared to those with normal and copy number duplicate genotypes. These data suggest that the functional copy number deletion in the PLA2G4A gene is associated with the risk of schizophrenia and clinical phenotypes by reducing the expression of cPLA2, which may be an indicator of susceptibility to schizophrenia.

Online monitoring of continuous aqueous two-phase flotation (ATPF) for the development of an autonomous control strategy

Aqueous two-phase flotation (ATPF) is a separation technique for isolating biological products such as enzymes from crude complex biosuspensions. The continuous operation mode of ATPF allows high throughput while maintaining a high separation efficiency. In this work, a laboratory plant for continuous ATPF with integrated online measurement technology is presented and ATPF experiments with the model enzyme phospholipase A2 are performed. Three electrical conductivity probes allow real time and spatially resolved characterization of phase mixing in the flotation tank caused by rising bubbles. UV/Vis spectroscopy is used to measure the enzyme concentration online at the top phase outlet. The equilibrium concentrations in the top and bottom phase are linearly dependent on the feed concentration, revealing a constant partition coefficient. The experimental results of this work provide the basis for the development of an autonomous feedback controller for the continuous ATPF process.

Lipidomics of phospholipase A2 reveals exquisite specificity in macrophages

Phospholipase A2 (PLA2) constitutes a superfamily of enzymes that hydrolyze phospholipids at their sn-2 fatty acyl position. Our laboratory has demonstrated that PLA2 enzymes regulate membrane remodeling and cell signaling by their specificity toward their phospholipid substrates at the molecular level. Recent in vitro studies show that each type of PLA2, including Group IVA cytosolic PLA2 (cPLA2), Group V secreted PLA2 (sPLA2), Group VIA calcium independent PLA2 (iPLA2) and Group VIIA lipoprotein-associated PLA2, also known as platelet-activating factor acetyl hydrolase, can discriminate exquisitely between fatty acids at the sn-2 position. Thus, these enzymes regulate the production of diverse PUFA precursors of inflammatory metabolites. We now determined PLA2 specificity in macrophage cells grown in cell culture, where the amounts and localization of the phospholipid substrates play a role in which specific phospholipids are hydrolyzed by each enzyme type. We used PLA2 stereospecific inhibitors in tandem with a novel UPLC-MS/MS-based lipidomics platform to quantify more than a thousand unique phospholipid molecular species demonstrating cPLA2, sPLA2, and iPLA2 activity and specificity toward the phospholipids in living cells. The observed specificity follows the in vitro capability of the enzymes and can reflect the enrichment of certain phospholipid species in specific membrane locations where particular PLA2’s associate. For assaying, we target 20:4-PI for cPLA2, 22:6-PG for sPLA2, and 18:2-PC for iPLA2. These new results provide great insight into the physiological role of PLA2 enzymes in cell membrane remodeling and could shed light on how PLA2 enzymes underpin inflammation and other lipid-related diseases.