346 



IMMUNO-CATALYSIS 



phosphorus from an aqueous emulsion of lecithin as a measure of 

 lecithinase activity. A lecithinase unit, arbitrarily defined, was that 

 quantity of enzyme which under the conditions prescribed above pro- 

 duced 0.1 ml. of acid-soluble phosphorus from lecithin in fifteen min- 

 utes at 37°C. The relationship between the minimum lethal dose, the 

 egg-yolk unitage and the lecithinase activity of toxins, respectively, of a 

 pool of toxins was 400, 200, and 210. Theriault (1945) carried out a 

 detailed study of the factors insuring the optimal potency of the a-toxin 

 based on lecithinase activity. His specifications differ from those pro- 

 posed by MacFarlane and Knight chiefly in the use of more lecithinase 

 and of more buffer, also in the use of a higher temperature (45 °C.) 

 incubation. 



Turhidometric Method. Lecithinase produces opalescence in some 

 samples of human serum both from normal and diseased persons. A 

 clear filtrate of lecitho-vitellin prepared by heating a saline suspension 

 of egg-yolk and filtering through a Seitz-filter has also been used as 

 substrate for this reaction. Following the detailed study of opalescence 

 by MacFarlane, Oakley and Anderson (1941), van Heyningen 



Lecithinase (a-Toxin) of CI. welchii 



CH.OCOR O- 



a-Lecithin iff!!^!!^^ CHpCOR + 0-P-OCH2CH2N+(CH3)3-FH+ 



+H2O 



CHoOH 



O 



Oleyl-stearyl- Choline phosphoric 



diglyceride acid 



(Non-hemolytic) 



H++HCO3 



^COst+HoO 



