182 IMMUNO-CATALYSIS 



egg white with relative ease would appear to account for the facts 

 described by Bayliss.* 



The ability of trypsin to digest the type specific M protein from 

 living streptococci is reported by Lancefield (1941). She stated that 

 the M substance in the living bacteria is readily accessible to the 

 action of proteolytic enzymes without injury to other vital functions 

 (viability, virulence and the ability of the multiplying streptococci to 

 synthesize M) of the living cells. This, she concluded, may be due to 

 its possible location near the outer surface of the streptococci. 



M is an unsymmetrical protein of about 41,000 molecular weight 

 (Pappenheimer, et at. 1942). The ratio of major to minor axis is at 

 least 20 to 1, which puts it into the class of "denatured" or unfolded 

 proteins. Since the process of extraction from streptococci (16 hours 

 at 56°C. with 0.05 N HCl containing 2 per cent sodium chloride) 

 and subsequent treatments with alcohol, etc. do not affect the sero- 

 logical type specificity of M, it is possible that the constitution of this 

 protein in its natural environment may be similar to that of the 

 isolated form. These facts may perhaps explain why M, of all the 

 other cellular proteins, is apparently selectively digested by trypsin. 



Impermeability of living cells to proteolytic enzymes as the cause 

 of the resistance of "living" proteins to these enzymes does not ac- 

 count for the resistance of extracellular native proteins to proteolytic 

 digestion. Anson and Mirsky (1933), and Anson (1938) reported that 

 hemoglobin denatured by salicylate is digested by trypsin which does 

 not attack native hemoglobin. The denatured hemoglobin was in- 

 soluble under the same conditions under which native hemoglobin 

 was soluble; it had the parahematin type of spectrum which is also 

 given by a solution of hemin in pyridine. When the denaturation of 

 hemoglobin by salicylate is reversed, the original properties of native 

 hemoglobin are restored, t 



Bawden and Pirie (1937) also found that crystalline tobacco mosaic 

 virus is resistant to proteolytic enzymes. They stated that no enzyme 



*In this connection an observation by Pozerski and Guelin Cl938a) is of impor- 

 tance. They found that raw egg white exercised no inhibitory effect on the gelatinase 

 activity of B. histolyticum. In contrast the proteolytic activity of this organism was 

 strongly inhibited by immune horse serum against B. histolyticum. This serum exer- 

 cised no inhibitory action on the proteolytic activity of closely related B. sforogenes. 



fin this connection it is to be noted that active bacteriophage and botulinal toxin 

 similar to native hemoglobin, are resistant to proteolytic enzymes (Kalmanson and 

 Bronfenbrenner, 1943^. 



