The main types of phospholipids present in erythrocytes, namely lysolecithin, lecithin, phosphatidyl ethanolamine, phosphatidyl serine and sphingomyelin, were found to be degraded by enzymes produced by parasitic and saprophytic leptospirae. No basic difference was found between the degradation of the phospholipids bound in serum lipoproteins and that of the phospholipids bound in the membranes of erythrocytes. The parasitic leptospirae were differentiated into two groups according to their ability to degrade the choline-containing phospholipids: (1) strains degrading lecithin and sphingomyelin, and (2) strains degrading neither lecithin nor sphingomyelin. The saprophytic leptospirae degraded lecithin but not sphingomyelin.

The activity of the enzymes of the different strains of leptospirae in degrading phospholipids was correlated with the haemolytic activity of the strains. Calcium ions were found to activate both the degradation of lecithin, phosphatidyl ethanolamine and phosphatidyl serine by saprophytic leptospirae and the haemolysis caused by these leptospirae. Calcium ions did not activate the degradation of erythrocyte phospholipids and the haemolysis caused by the parasitic leptospirae.

These findings suggest (1) that the haemolytic action of leptospiral haemolysin is due to an enzymatic degradation of phospholipids in the erythrocyte membrane, (2) that the “haemolysin” of leptospirae consists of more than one enzyme (phospholipase), (3) that the enzymes constituting the “haemolysin” of the parasitic leptospirae differ from those constituting that of the saprophytic leptospirae, and (4) that two main factors determine the susceptibility of erythrocytes from different animal species to the haemolytic action of leptospirae, namely, the enzyme composition of the haemolysin and the phospholipid composition of the erythrocyte membrane.


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