Isolation of a hemolytic, toxic phospholipase from the venom of the Australian red-bellied black snake ( Pseudechis porphyriacus)

Abstract

A weak toxin was isolated from the venom of the Australian red-bellied black snake, Pseudechis porphyriacus, by ion-exchange chromatography on Bio-Rex 70, followed by gel filtration on Sephadex G-50. The toxin, pseudexin, accounts for 25% of the venom and has an ld 50 (i.p.) of 480 μg/kg mouse. It is a polypeptide of 143 amino acid residues and has a formula weight of 16,659. Pseudexin has phospholipase A (phosphatidate acyl-hydrolase, EC 3.1.1.4) activity. Modification of the toxin with p-bromophenacyl bromide resulted in a 99·9% loss of phospholipase activity and a reduction of its toxicity. The toxin, like other phospholipases, caused indirect hemolysis of washed erythrocytes. In addition, pseudexin directly hemolysed erythrocytes under conditions in which phospholipases are normally non-hemolytic.