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 mu l/g mouse). By gel filtration on Fractogel (TSK HW 50f) foll owed by cation-exchange chromatography on Mono S column, three toxins desig nated as verutoxin 1, 2a and 2b (VT-1, VT-2a and VT-2b) were isolated from the venom. The toxin VT-I had a molecular mass of 34,982 Da and an LD50 val ue of 3.61 mu g/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 o nly 14 Da (33,360 and 33,374 Da, respectively) and had a similar toxicity i n mice (LD50 = 0.87 mu g/g mouse). All three toxins were capable of catalyz ing the hydrolysis of emulsified phospholipids and lysophosphatide, but not sphingomyelin. Analysis of the hydrolyzed products (fatty acid and lyse-co mpound) by a liquid chromatography/mass spectrometer revealed that the toxi ns liberates fatty acid mainly from the 1-position of the synthetic phospho lipid. This result indicates that verutoxins possess phospholipase A(1) act ivity. Toxin VT-I showed higher phospholipase activity than VT-2a and 2b. H owever, the latter toxins exhibited much higher direct hemolytic activity t oward the mouse red blood cells. Vespid phospholipases are known as one of the three major venom allergens in many species of wasps. Our studies indic ate that vespid phospholipases A(1), in addition to acting as allergens, po ssess direct toxic actions that may also cause death in animals. Toxin VT-2 a and 2b which possess potent hemolytic activity and high lethality in mice may act as the lethal factor of V. verutina venom. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.