[Amino acid sequence of orientotoxins I and II from the venom of the hornet Vespa orientalis].

Orientotoxin I, a neurotoxin of presynaptic effect having a lysophospholipase activity, and orientotoxin II, a highly toxic phospholipase A2, were isolated from the hornet Vespa orientalis venom, and their primary structures were determined. Despite their different functional activity, orientotoxin I and II proved to be structural homologues, differing significantly in the amino acid sequence from well-known toxic phospholipase from other sources.

[Purification and properties of lysophospholipase from the venom of the giant hornet Vespa orientalis].

Using biospecific chromatography on polylysocephamide, a toxic phospholipase possessing a presynaptic effect on neuromuscular preparations was isolated from the venom of the giant hornet Vespa orientalis. The enzyme was shown to possess a high hydrolytic activity towards 1-acyllysophosphatidylcholine within a narrow pH range (pH optimum 7.5).

[Hemolytic effect of phospholipase A2 and orientotoxin from venom of the great hornet, Vespa orientalis].

The effect of toxic phospholipase A2 and orientotoxin from the venom of the giant hornet Vespa orientalis on human erythrocytes was studied. It was shown that these venom components are potent hemolytic agents, the efficiency of the latter being by about two orders of magnitude as high as that of phospholipase A2. The hemolytic function of the both components is enhanced in the presence of low concentrations of Ca2+, whereas high concentrations of this cation exert an inhibiting action.

[Low molecular weight peptides from the venom of the giant hornet Vespa orientalis. Structure and function].

Three 14-member linear peptides (HR-1, HR-2 and HR-3) capable of degranulating mast cells and thus initiating histamine release were isolated from the venom of the giant hornet Vespa orientalis, using reverse phase high performance liquid chromatography. The complete amino acid sequence of the peptides HR-1 and HR-2 molecules and partial structure of peptide HR-3 were determined, using automatic degradation by the Edman method. It was shown that peptide HR-1 at relatively low concentrations (2-20 micrograms/ml) selectively liberated histamine from rat mast cells and, when taken at higher doses (50-100 micrograms/ml), exerted a non-selective cytotoxic action.

[Fluorescence proper of phospholipase A2 and orientotoxin from the venom of the giant hornet in the presence of ionic modulators of their membrane activity].

The own fluorescence of phospholipase A2 and orientotoxin at interaction of these components from Oriental hornet venom with calcium, strontium, lantan, magnesium ions has been investigated. Ca2+, La3+, Sr2+--activators of phospholipase activity--increase the quantum output of fluorescence. In the presence of Ca2+ the temperature of semitransitional process of thermoinactivation of investigated polypeptides increases by 2 degrees C.

[Determination of phospholipase A2 and lysophospholipase A1 in a mixture].

The phospholipase A2 and lysophospholipase A1 activities were determined in various mixtures. When estimating the phospholipase A2 activity in venoms of snakes and insects the known methods based on measuring a change in the optical density of the egg yolk suspension are not acceptible if in investigated object besides phospholipases lysophospholipases are present (venoms of viper and giant hornet). In this case anomalous curves of changes in the system optical density in time are obtained.

[Properties of phospholipase A2 from the venom of the large hornet Vespa orientalis].

Some properties (catalytic and hemolytic activity, pH and temperature optima, stability, substrate specificity, effects of detergents and metal ions, N-terminal sequence, chemical modification of histidine in the enzyme active center, etc.) of phospholipase A2 from hornet (Vespa orientalis) venom were studied. It was shown that phospholipase A2 from hornet venom differs essentially from other enzymes of this species in terms of stability, catalytic properties and structural features.

[Orientotoxin--a new presynaptic neurotoxin from the venom of the giant hornet Vespa orientalis].

Orientotoxin, a novel presynaptically acting neurotoxin from the venom of giant hornet Vespa orientalis, has been isolated by gel filtration and ion exchange chromatography and characterized. The toxin has a molecular mass of 18,000. Highly purified preparations of orientotoxin possessed clearly manifested lysophospholipase activity and can block both induced and spontaneous release of neurotransmitter from the presynaptic nerve membrane.

[Isolation and purification of two lipolytic enzymes from Vespa orientalis venom].

Two lipolytic enzymes--phospholipase A2 and lysophospholipase A1 were isolated in individual state from the venom of the big hornet Vespa orientalis. It was shown that these enzymes have approximately the same molecular weight of about 26 000, but differ in their electrophoretic mobilities. Besides, the enzymes possess marked specificity to lecithin and L-lysolecithin, respectively.

[Characterization of some membrane-active components of Vespa orientalis venom].

The molecular weight distribution of the components of giant hornet (Vespa orientalis) venom was studied, using gel-filtration on a column with Sephadex G-50. The effects of the venom and its constituent fractions on the permeability and stability of artificial bilayer phospholipid membranes, potassium ions release from the erythrocytes and mitochondrial oxidative phosphorylation parameters, as well as on the activity and stability of polyenzymic systems of the mitochondrial respiratroy chain, were studied. The data obtained suggest that the high molecular weight fractions contain phospholipases, whose activities are much higher than those of presently known venoms.