Hornetin: the lethal protein of the hornet (Vespa flavitarsus) venom

Giant hornet (Vespa mandarinia) venomous phospholipases. The purification, characterization and inhibitory properties by biscoclaurine alkaloids

Two species of giant hornet phospholipase B (PLB), alpha and beta, were purified from the venom of Vespa mandarinia. The purification procedure was simplified by two steps of column chromatographies, Sephadex G-100 and SP-Sepharose. The molecular sizes of PLB alpha and beta were 29.5 and 26.0 kDa, respectively. The isoelectric point of alpha and beta enzymes were pH 10.6 and 10.7, respectively. The temperature optimum for egg yolk lecithin was a broad peak at 40-60 degrees C for both enzymes. Amino acid compositions of both enzymes were high contents of aspartic acid, glycine, leucine, lysine and other aliphatic amino acids. Cystine was similar amounts to other species of phospholipases (PLs). The K(m) values of alpha and beta enzymes were 8.29 and 7.53 mg/ml for egg yolk lecithin, respectively. In the catalytic specificity for L-alpha-phosphatidylcholine-beta-oleoil-gamma-palmitoil, the K(m) values of alpha enzyme for gamma-palmitoil and beta-oleoil residues were 0.528 and 1.392 mM, respectively. While the K(m) values of beta enzyme for gamma-palmitoil and beta-oleoil residues were 7.91 and 2. 68 mM, respectively. Both alpha and beta enzymes were inhibited strongly by cepharanthine. The lecithin hydrolysis of alpha enzyme was competitively inhibited, but beta enzyme was uncompetitive. Cepharanthine also inhibited noncompetitively PLA(2)s of bovine pancreas, bee venom and Naja mossambica mossambica.

Three toxins with phospholipase activity isolated from the yellow-legged hornet (Vespa verutina) venom

The yellow-legged hornet, Vespa verutina, is widely distributed in both the mountain area and the suburbs of Taiwan and possesses highly toxic venom (LD50=0.02 microl/g mouse). By gel filtration on Fractogel (TSK HW 50f) followed by cation-exchange chromatography on Mono S column, three toxins designated as verutoxin 1, 2a and 2b (VT-1, VT-2a and VT-2b) were isolated from the venom. The toxin VT-1 had a molecular mass of 34,982 Da and an LD50 value of 3.61 microg/g mouse. Toxin VT-2a and 2b were more basic and more toxic than VT-1. VT-2a and 2b were isotoxins with molecular masses differing in only 14 Da (33,360 and 33,374 Da, respectively) and had a similar toxicity in mice (LD50=0.87 microg/g mouse). All three toxins were capable of catalyzing the hydrolysis of emulsified phospholipids and lysophosphatide, but not sphingomyelin. Analysis of the hydrolyzed products (fatty acid and lyso-compound) by a liquid chromatography/mass spectrometer revealed that the toxins liberates fatty acid mainly from the 1-position of the synthetic phospholipid. This result indicates that verutoxins possess phospholipase A1 activity. Toxin VT-1 showed higher phospholipase activity than VT-2a and 2b. However, the latter toxins exhibited much higher direct hemolytic activity toward the mouse red blood cells. Vespid phospholipases are known as one of the three major venom allergens in many species of wasps. Our studies indicate that vespid phospholipases A1, in addition to acting as allergens, possess direct toxic actions that may also cause death in animals. Toxin VT-2a and 2b which possess potent hemolytic activity and high lethality in mice may act as the lethal factor of V. verutina venom.

Local edema induced by the black-bellied hornet (Vespa basalis) venom and its components

The black-bellied hornet, Vespa basalis, is one of the most dangerous species of wasp in Taiwan. The hornet venom possesses a potent edema-inducing activity in addition to its lethal cardiovascular effect. Rat hind-paw edema induced by the venom was inhibited significantly by antiserotonin compounds (cyproheptadine and methysergide) but not by antihistaminics (chlorpheniramine and diphenhydramine), betamethasone, cromolyn, indomethacin plus nordihydroguaiaretic acid, cellulose sulfate, aprotinin or captopril. However, chlorpheniramine or betamethasone, when given in combination with cyproheptadine, showed a significant further inhibition of the venom-induced edema. Pretreating the rat with compound 48/80 reduced the edematous response to the venom. Four venom components, i.e. the lethal protein, mastoparan B, fraction 3 (containing protease) and fraction 15 (containing serotonin) were involved in the edematous effect of the venom. Paw edema induced by the crude venom and its protein components (lethal protein, mastoparan B and fraction 3) was similar in their responses to antiserotonin compounds and antihistamine (inhibited by cyproheptadine and methysergide but not by chlorpheniramine), while that induced by fraction 15 was inhibited by both. It is postulated that upon hornet stings, fraction 15 is acting as an exogenous serotonin, while the protein components, especially the lethal protein, are responsible for the release of endogenous autacoids in which serotonin plays the most important role in inducing local edema.

Comparative study of amino acid composition in an extract from hornet venom sacs: high content of neuroactive amino acids in Vespa

The amino acid compositions of extracts from the venom sacs of Vespa mandarinia, V. xanthoptera, V. tropica, V. analis and Vespula lewisi were analyzed. omega-Amino acids, which are inhibitory neurotransmitters, such as gamma-amino-n-butyric acid, taurine, beta-alanine and glycine, were predominant components in Vespa, but a minor component in Vespula. Glutamic acid, an aminergic excitatory neurotransmitter, was present in large quantities. Leucine, an insect autotoxin, was detected. Arginine was found in all the venoms and glutamine was also abundant. Tryptophan and histidine, precursors of serotonin and histamine, respectively, were also found. Thus, neuroactive amino acids that may exert inhibitory effects on insects neuronal axons and neuromuscular junctions were present in large amounts, and may facilitate paralysis of insect prey.

Purification and characterization of a lethal protein with phospholipase A1 activity from the hornet (Vespa basalis) venom

The hornet, Vespa basalis, is one of the most dangerous species of wasps found in Taiwan. The insect is aggressive and its venom is highly toxic. By gel filtration on a Fractogel TSK HW 50 column followed by cation-exchange chromatography on CM-Trisacryl M, a lethal protein was purified from the venom. It has a molecular mass of about 32 kDa and an i.v. LD50 value of 0.32 micrograms/g mouse. The toxin is capable of catalyzing the hydrolysis of emulsified phospholipids but not sphingomyelin. Analysis of the 1H-NMR spectra of the substrates and its hydrolytic products revealed that the toxin liberates fatty acid from the 1-position of sn-3-phosphoacylglycerols. This result indicates that the toxin possesses phospholipase A1 activity. The toxin exhibits an extremely potent hemolytic activity in washed red cells and diluted whole blood (HC50 = 0.09 micrograms/ml in mouse). The potency of direct hemolysis is about 100-times that of a basic phospholipase A2 from Naja nigricollis venom and about 1000-times that of a cardiotoxin from Naja naja atra venom. A positive correlation between the hemolytic activity and lethality of the toxin was found in three species of animals (mouse, rat and guinea pig). In the in vivo study, the toxin caused a marked increase in the plasma K+ concentration and a hyperkalemic change in the ECG of the treated rat. Hyperkalemia resulting from the hemolytic action of the toxin appears to be the main cause of death in the animal.