cDNA cloning and sequencing of phospholipase A2 from the pyloric ceca of the starfish Asterina pectinifera

Practical Euthanasia Method for Common Sea Stars (Asterias rubens) That Allows for High-Quality RNA Sampling

Sea stars in research are often lethally sampled without available methodology to render them insensible prior to sampling due to concerns over sufficient sample quality for applied molecular techniques. The objectives of this study were to describe an inexpensive and effective two-step euthanasia method for adult common sea stars (Asterias rubens) and to demonstrate that high-quality RNA samples for further use in downstream molecular analyses can be obtained from pyloric ceca of MgCl₂-immersed sea stars. Adult common sea stars (n = 15) were immersed in a 75 g/L magnesium chloride solution until they were no longer reactive to having their oral surface tapped with forceps (mean: 4 min, range 2-7 min), left immersed for an additional minute, and then sampled with sharp scissors. RNA from pyloric ceca (n = 10) was isolated using a liquid-liquid method, then samples were treated with DNase and analyzed for evaluation of RNA integrity number (RIN) for assessment of the quantity and purity of intact RNA. Aversive reactions to magnesium chloride solution were not observed and no sea stars regained spontaneous movement or reacted to sampling. The calculated RIN ranged from 7.3-9.8, demonstrating that the combination of animal welfare via the use of anesthesia and sampling for advanced molecular techniques is possible using this low-cost technique.

Conodipine-P1-3, the First Phospholipases A2 Characterized from Injected Cone Snail Venom

The phospholipase A₂ (PLA₂s) superfamily are ubiquitous small enzymes that catalyze the hydrolysis of phospholipids at the sn-2 ester bond. PLA₂s in the venom of cone snails (conodipines, Cdpi) are composed of two chains termed as alpha and beta subunits. Conodipines are categorized within the group IX of PLA₂s. Here we describe the purification and biochemical characterization of three conodipines (Cdpi-P1, -P2 and -P3) isolated from the injected venom of Conus purpurascens Using proteomics methods, we determined the full sequences of all three conodipines. Conodipine-P1-3 have conserved consensus catalytic domain residues, including the Asp/His dyad. Additionally, these enzymes are expressed as a mixture of proline hydroxylated isoforms. The activities of the native Conodipine-Ps were evaluated by conventional colorimetric and by MS-based methods, which provide the first detailed cone snail venom conodipine activity monitored by mass spectrometry. Conodipines can have medicinal applications such inhibition of cancer proliferation, bacterial and viral infections among others.

Prostaglandins and Other Eicosanoids in Insects: Biosynthesis and Biological Actions

This essay reviews the discoveries, synthesis, and biological significance of prostaglandins (PGs) and other eicosanoids in insect biology. It presents the most current - and growing - understanding of the insect mechanism of PG biosynthesis, provides an updated treatment of known insect phospholipase A2 (PLA2), and details contemporary findings on the biological roles of PGs and other eicosanoids in insect physiology, including reproduction, fluid secretion, hormone actions in fat body, immunity and eicosanoid signaling and cross-talk in immunity. It completes the essay with a prospectus meant to illuminate research opportunities for interested readers. In more detail, cellular and secretory types of PLA2, similar to those known on the biomedical background, have been identified in insects and their roles in eicosanoid biosynthesis documented. It highlights recent findings showing that eicosanoid biosynthetic pathway in insects is not identical to the solidly established biomedical picture. The relatively low concentrations of arachidonic acid (AA) present in insect phospholipids (PLs) (< 0.1% in some species) indicate that PLA2 may hydrolyze linoleic acid (LA) as a precursor of eicosanoid biosynthesis. The free LA is desaturated and elongated into AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce PGH2, which is then isomerized into cell-specific PGs. In particular, PGE2 synthase recently identified converts PGH2 into PGE2. In the cross-talks with other immune mediators, eicosanoids act as downstream signals because any inhibition of eicosanoid signaling leads to significant immunosuppression. Because host immunosuppression favors pathogens and parasitoids, some entomopathogens evolved a PLA2 inhibitory strategy activity to express their virulence.

Enzymatic properties of starfish phospholipase A2 and its application

Industrial phospholipase A2 (PLA2) mainly produced from porcine pancreas is used for production of lysolecithin which is well known as an excellent natural emulsifier for food, cosmetic, and pharmaceutical industries. Since the outbreak of bovine spongiform encephalopathy (BSE) or religious tradition, it is hoped that the new sources of PLA2, as well as other enzymes and proteins, will be developed instead of mammal. From these backgrounds, we studied for PLA2 from marine organisms and found that starfish Asterina pectinifera PLA2 possesses extremely high activity and characteristic polar-group specificity comparing with commercially available PLA2 from porcine pancreas. Therefore, it was suggested that the starfish A. pectinifera would be a potential source of PLA2, and the PLA2 can be utilized as alternative enzyme of mammalian PLA2.

Mackerel trypsin purified from defatted viscera by supercritical carbon dioxide

Viscera of mackerel (Scomber sp.) were defatted by supercritical carbon dioxide (SCO(2)) treatment. Trypsin (SC-T) was then extracted from the defatted powder and purified by a series of chromatographies including Sephacryl S-200 and Sephadex G-50. The purified SC-T was nearly homogeneous on SDS-PAGE, and its molecular weight was estimated as approximately 24,000 Da. N-terminal twenty amino acids sequence of SC-T was IVGGYECTAHSQPHQVSLNS. The specific trypsin inhibitors, soybean trypsin inhibitor and TLCK, strongly inhibited the activities of SC-T. The pH and temperature optimums of SC-T were at around pH 8.0 and 60°C, respectively, using N(α)-p-tosyl-L-arginine methyl ester as a substrate. The SC-T was unstable below pH 5.0 and above 40°C, and it was stabilized by calcium ion. These enzymatic characteristics of SC-T were the same as those of other fish trypsins, especially spotted mackerel (S. borealis) trypsin, purified from viscera defatted by acetone. Therefore, we concluded that the SCO(2) defatting process is useful as a substitute for organic solvent defatting process.

Purification and characterization of the biological effects of phospholipase A(2) from sea anemone Bunodosoma caissarum

Sea anemones contain a variety of biologically active substances. Bunodosoma caissarum is a sea anemone from the Cnidaria phylum, found only in Brazilian coastal waters. The aim of the present work was to study the biological effects of PLA(2) isolated from the sea anemone B. caissarum on the isolated perfused kidney, the arteriolar mesenteric bed and on insulin secretion. Specimens of B. caissarum were collected from the São Vicente Channel on the southern coast of the State of São Paulo, Brazil. Reverse phase HPLC analysis of the crude extract of B. caissarum detected three PLA(2) proteins (named BcPLA(2)1, BcPLA(2)2 and BcPLA(2)3) found to be active in B. caissarum extracts. MALDI-TOF mass spectrometry of BcPLA(2)1 showed one main peak at 14.7 kDa. The N-terminal amino acid sequence of BcPLA(2)1 showed high amino acid sequence identity with PLA(2) group III protein isolated from the Mexican lizard (PA23 HELSU, HELSU, PA22 HELSU) and with the honey bee Apis mellifera (PLA(2) and 1POC_A). In addition, BcPLA(2)1 also showed significant overall homology to bee PLA(2). The enzymatic activity induced by native BcPLA(2)1 (20 microg/well) was reduced by chemical treatment with p-bromophenacyl bromide (p-BPB) and with morin. BcPLA(2)1 strongly induced insulin secretion in presence of high glucose concentration. In isolated kidney, the PLA(2) from B. caissarum increased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate, and sodium, potassium and chloride levels of excretion. BcPLA(2)1, however, did not increase the perfusion pressure on the mesenteric vascular bed. In conclusion, PLA(2), a group III phospholipase isolated from the sea anemone B. caissarum, exerted effects on renal function and induced insulin secretion in conditions of high glucose concentration.

Molecular cloning of two toxic phospholipases A2 from the crown-of-thorns starfish Acanthaster planci venom

The full-length cDNAs encoding two toxic phospholipases A2 (AP-PLA2-I and -II) from the crown-of-thorns starfish Acanthaster planci venom were individually cloned by RT-PCR, 3'RACE and 5'RACE. In common with both AP-PLA2s, the precursor protein is composed of a signal peptide, a propeptide and a mature protein (136 and 135 residues for AP-PLA2-I and -II, respectively). The four motifs (Ca2+-binding loop, Ca2+-binding site, active site and catalytic network) characteristic of groups I and II PLA2s are well conserved in both AP-PLA2s. In addition to this, the presence of the elapid and pancreatic loops and the involvement of a propeptide in the precursors suggested that AP-PLA2s are highly analogous to the group IB PLA2s. However, when compared to the amino acid sequence of bovine pancreatic PLA2, the representative group IB PLA2, AP-PLA2s require some amino acid insertions and deletions in the region 76-100, as previously observed for the starfish Asterina pectinifera PLA2s. Furthermore, the phylogenetic tree made clearly demonstrated that AP-PLA2s and A. pectinifera PLA2s are distinguishable from the group IB PLA2s as well as other PLA2s, being classified into a new group.

Molecular cloning, expression, and characterization of secretory phospholipase A2 in tobacco

Phospholipase A2 (PLA2) activity was investigated in various tissues of tobacco (Nicotiana tabacum). PLA2 activity in the flower was 15 times higher than that in the leaf, stem, and root. PLA2 activity in the flower appears to have originated from both Ca2+-dependent and -independent PLA2. A cDNA clone for protein with homology to animal secretory PLA2 (sPLA2), denoted as Nt PLA2, was isolated from the tobacco flower. The cDNA of Nt PLA2 encoded a mature protein of 127 amino acid residues with a putative signal peptide of 30 residues. The amino acid sequence for mature Nt PLA2 contains 12 cysteines, a Ca2+ binding loop, and a catalytic domain that are commonly conserved in animal sPLA2. The Nt PLA2 mRNA was mainly expressed in the root and stem of tobacco. The recombinant Nt PLA2 was expressed as a fusion protein with thioredoxin in Escherichia coli. From the bacterial cell lysate, the fusion protein was recovered in soluble form and cleaved by Factor Xa proteinase. Then the recombinant mature Nt PLA2 was purified by ion exchange chromatography. It was discovered that the purified Nt PLA2 essentially requires Ca2+, for the enzyme activity when the activity was determined using mixed-micellar phospholipid substrates with sodium cholate. The optimal activity of Nt PLA2 was at pH 8-10 when PC was used as a substrate.

Phospholipase A2 in Cnidaria

Phospholipase A2 (PLA2) is an enzyme present in snake and other venoms and body fluids. We measured PLA2 catalytic activity in tissue homogenates of 22 species representing the classes Anthozoa, Hydrozoa, Scyphozoa and Cubozoa of the phylum Cnidaria. High PLA2 levels were found in the hydrozoan fire coral Millepora sp. (median 735 U/g protein) and the stony coral Pocillopora damicornis (693 U/g) that cause skin irritation upon contact. High levels of PLA2 activity were also found in the acontia of the sea anemone Adamsia carciniopados (293 U/g). Acontia are long threads containing nematocysts and are used in defense and aggression by the animal. Tentacles of scyphozoan and cubozoan species had high PLA2 activity levels: those of the multitentacled box jellyfish Chironex fleckeri contained 184 U/g PLA2 activity. The functions of cnidarian PLA2 may include roles in the capture and digestion of prey and defense of the animal. The current observations support the idea that cnidarian PLA2 may participate in the sting site irritation and systemic envenomation syndrome resulting from contact with cnidarians.

A novel phospholipase A2/esterase from hyperthermophilic archaeon Aeropyrum pernix K1

An open reading frame of the hyperthermophilic archaeon Aeropyrum pernix K1 APE2325, which composed of 474 bases, was cloned and expressed in Escherichia coli BL21 (DE3) Codon Plus-RIL. The recombinant protein was purified by Ni-chelation affinity chromatography. It showed a single band with a molecular mass of 18kDa in SDS-PAGE. The purified enzyme exhibited both phospholipase A(2) and esterase activities with the optimal catalytic temperature at 90 degrees C. The enzyme activity was Ca(2+)-independent. Kinetic analysis revealed its Km, k cat, and Vm for the p-nitrophenyl propionate substrate were 103microM, 39s(-1), and 249micromol/min/mg, respectively. The recombinant protein was thermostable and its half-life at 100 degrees C was about 1h.

Phospholipase A2 in porifera

Phospholipase A2 (PLA2) catalytic activity was measured in aqueous extracts of 83 freeze-dried specimens representing 55 marine sponge species collected from the east coast of Australia including the Great Barrier Reef. High levels (>500 u/l) of PLA2 activity (defined as the amount of activity that releases 1 micromol of fatty acid per min) were found in four out of 55 species (7%), moderate activities (100-499 u/l) in 6/55 (11%), low activities (1-99 u/l) in 11/55 (20%) and no PLA2 activity in 34/55 (62%). Species with high PLA2 activity levels included Cymbastela coralliophila (2118 u/l, specific activity 10,590 u/g of protein), Acanthella cavernosa (1318 u/l, specific activity 2470 u/g), Spirastrella vagabunda (1036 u/l, specific activity 1727 u/g and Theonella swinhoei (567 u/l, specific activity 354 u/g). It was postulated that poriferan PLA2 may be involved in eicosanoid metabolism and antimicrobial and toxic defence of the animal.

Cloning of a novel phospholipase A2 from the cnidarian Adamsia carciniopados

PLA2 catalytic activity was detected in homogenised tissues, including tentacles and acontia (structures for preying and defence, respectively), of the sea anemone Adamsia carciniopados. Nested reverse transcription polymerase chain reaction (RT PCR) with degenerate primers and rapid amplification of cDNA ends (RACE) were used to clone a novel phospholipase A2 from Adamsia carciniopados (AcPLA2). AcPLA2 contains a putative prepropeptide of 37 residues, ending with a basic doublet followed by a mature protein of 119 amino acids, including 12 cysteines. AcPLA2 displays only 30-42% similarity with other known secretory PLA2s (sPLA2). C-terminal extension, typical of groups II and X PLA2s, is absent. Predicted molecular weight and pI of the mature protein are 13.5 kDa and 9.1, respectively. Structural features and phylogenetic analysis set AcPLA2 apart from the known sPLA2s and define this molecule in the ancient metazoan phylum Cnidaria as a member of a new class of sPLA2s.

Bacterial expression and characterization of starfish phospholipase A(2)

Phospholipase A(2) (PLA(2)) from the pyloric ceca of the starfish Asterina pectinifera showed high specific activity and characteristic substrate specificity, compared with commercially available PLA(2) from porcine pancreas. To investigate enzymatic properties of the starfish PLA(2) in further detail, we constructed a bacterial expression system for the enzyme. The starfish PLA(2) cDNA isolated previously (Kishimura et al., 2000b. cDNA cloning and sequencing of phospholipase A(2) from the pyloric ceca of the starfish Asterina pectinifera. Comp. Biochem. Physiol. 126B, 579-586) was inserted into the expression plasmid pET-16b and the PLA(2) protein was expressed in Escherichia coli BL21 (DE3) by induction with isopropyl-beta-D(-)-thiogalactopyranoside. The recombinant PLA(2) produced as inclusion bodies was dissociated with 8 M urea and 10 mM 2-mercaptoethanol and renatured by dialyzing against 10 mM Tris--HCl buffer (pH 8.0). Renatured PLA(2) was purified by subsequent column chromatographies on DEAE--cellulose (DE-52) and Sephadex G-50. Although an N-terminal Ser in the native starfish PLA(2) was replaced by an Ala in the recombinant PLA(2), the recombinant enzyme showed essentially the same properties as did the native PLA(2) with respect to specific activity, substrate specificity, optimum pH and temperature, and Ca(2+) requirement.