SUMMARY: Purified gamma haemolysin of was characterized in relation to the alpha, beta and delta haemolysins. The sedimentation coefficient of the gamma lysin was 2–65, somewhat higher than the values of 1.4 for freshly purified alpha lysin and 1.8 for the beta lysin. The molecular weight of gamma lysin determined by gel filtration was 45000 daltons. The pI of gamma lysin was 6.0, while that of the alpha, beta and delta lysins ranged from 8.5 to 9.6.

The amino acid analysis of gamma lysin was characterized by low levels of methionine and histidine. Methionine was, however, the -terminus, which suggested that all of the amino acid might be involved in the -terminal group.

The gamma lysin was immunologically distinct from the alpha, beta and delta lysins by quantitative precipitin tests; in Ouchterlony agar gel diffusion tests, single lines of precipitation were observed which showed no evidence of cross-reactions amongst the four haemolysins.

Gamma, beta and delta lysins had no effect in mice when injected at increasing doses ranging from 0 to 100 μg. The alpha lysin killed mice, the LD dose being 0.68 ± 0.12 μg, or 27 to 34 μg/kg mouse tissue. Gamma lysin was, however, lethal for guinea pigs when 50 μg quantities were injected intracardially. Gamma lysin also lysed human leucocytes and destroyed C-6 (human lymphoblast) cells.

Some nitrogen and phosphorus was released from human erythrocyte membranes treated with gamma lysin, when compared to untreated cells, and the rate of this release was linear over a 3 h period. Gamma lysin had no detectable effect on phospholipids extracted from erythrocytes or on lipid-free membrane protein. However, the haemolytic reaction was inhibited by erythrocyte membranes when these were added to lysin-red cell suspensions. Furthermore, human red cell phospholipids competitively inhibited haemolysis. Haemolysis was also inhibited by EDTA and activity could be restored by dialysis. The haemolytic reaction required sodium ions.


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