The haemolytic effect of phallolysin

Abstract

Phallolysin from the toadstool, Amanita phalloides, is a basic protein that causes direct haemolysis of red cells. The dose-response curve is steep; the pH optimum is in the weakly acid range. The rate of haemolysis increases with the concentration of the lysin, the optimal temperature is 20°C. The percentage haemolysis-time curves are S-shaped. Haemolysis is of the non-osmotic type. Ca²⁺ is not required but inhibits haemolysis in a concentration-dependent fashion, as do Mg²⁺ and Zn²⁺. The red cell sensitivity of various animal species decreases in the following sequence: mouse > rabbit=guinea pig > rat > man > dog ≃ pig > sheep-cattle. Red cells of cattle and sheep are largely resistant. Phallolysin is virtually not consumed on haemolysis: the amount of haemoglobin released increases with the number of red cells applied; on repeated addition of fresh red cells the haemolysate retains its full activity. Phallolysin is not inhibited by serum, albumin, cholesterol, lecithin, cephalin or sphingomyelin; inhibition by red cell ghosts of phallolysin haemolysis is considerably less than that of digitonin haemolysis. At sublytic concentrations phallolysin, unlike benzalkonium chloride, liberates practically no membrane lipids from human red cells. Surface activity of phallolysin does not exceed that of bovine serum albumin—A saponin-like interaction with cholesterol as the basic mechanism of haemolysis can be disregarded. There is also no evidence suggesting a detergent-like effect.