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The Lecithinase of Bacillus cereus and its Comparison with Clostridium welchii α-toxin
Abstract
Summary: Bacillus cereus and B. mycoides produce lecithinases which split lecithin into phosphorylcholine and a diglyceride in the same way as the lecithinase (α-toxin) of Clostridium welchii. These enzymes also possess most of the biological activities associated with Cl. welchii α-toxin, e.g. produce the Nagler reaction and the egg-yolk reaction, lyse red blood cells, and are dermonecrotizing and lethal.
The enzymes are activated by Ca and Mg ions, but inhibited by Na, K, NH4 ferric and Al ions. Optimal enzyme activity requires the presence of Ca ions within a narrow range of concentration of 1–4 × 10−3 m. It is interesting that at this concentration of Ca ion lecithin flocculates most readily from its emulsion. The enzyme thus seems to have a maximal affinity for lecithin when the latter adsorbs an optimal amount of Ca ion in reaching its isoelectric point.
Like the Cl. welchii lecithinase, the B. cereus lecithinase is fairly resistant to heat. The lysis of red blood cells and the hydrolysis of free lecithin by B. cerBus lecithinase was strongly inhibited by normal sera of all the animals tested. But when lecithin was bound in egg-yolk lipoproteins, its hydrolysis by the enzyme was unaffected by normal serum. Specific serum, on the other hand, was capable of inhibiting the hydrolysis of both free lecithin and protein-bound lecithin. The B. cereus and B. mycoides lecithinases are immunologically related, but they are not so related to Cl. welchii lecithinase.
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© Society for General Microbiology, 1949