The Chemistry of Diphtheria Toxin Produced in Synthetic Mediums

Chemical tests indicate that a protein is synthesized simultaneously with the production of toxin by diphtheria bacilli cultured in a synthetic medium. Experimental evidence supporting the view that the toxic fraction is identical with, or closely associated with, a protein is as follows: 1. In an electric field both toxin and protein migrate to the anode at$P_{H}$4.05 and to the cathode at$P_{H}$3.75. 2. The protein and the toxin are simultaneously destroyed by the enzymes trypsin and pepsin, as shown by quantitative chemical analyses. The slightly retarded action of neutral trypsin, as compared with the action of alkaline trypsin, in destroying the toxin might be taken as evidence that the toxic fraction is a whole protein. Conclusive evidence of the protein nature of diphtheria toxin must wait on the production of a crystalline protein toxin.