SELMAN A. WAKSMAN 275 



lyze proteoses, peptones, and various other polypeptides to amino acids; (3) the 

 amidases which attack the amino acid molecule with the formation of ammonia. 



Bacteria vary greatly in their ability to form proteolytic enzymes. Some form 

 true proteases, similar to the animal trypsin; others are unable to form enzymes which 

 act upon true proteins, but form ereptases. Although the bacterial proteases are 

 usually classified with animal trypsin, due to the fact that they are sensitive to acids 

 and that they act best at neutral or alkaline reactions, they are not identical with 

 this enzyme.' Some bacteria produce both trypsin-like and erepsin-like enzymes.^ 

 The formation of proteolytic enzymes by bacteria in culture media is independent 

 of the presence of proteins in the medium, the gelatin-liquefying enzyme being pro- 

 duced by various bacteria in simple, non-protein media just as abundantly, although 

 not quite so rapidly, as in complex protein media. The reaction of the medium affects 

 enzyme formation only in so far as it influences the growth of the bacteria.^ 



Bacteria vary also greatly in their capacity to form autolytic enzymes. The ca- 

 pacity of bacteria to produce proteolytic enzymes has frequently been used for diag- 

 nostic purposes. Here belong the various tests of liquefaction of gelatin, coagulated 

 egg-albumen and blood serum, milk coagulation and clarification, etc. Of special 

 interest in this connection is the role of proteolytic enzymes in the formation 

 of toxins by bacteria. Some investigators'' consider bacterial toxins to be not spe- 

 cific secretory products of the metabolism of the particular organisms, but biochemi- 

 cal transformation products of the constituents of the medium, as a result of the 

 transformation of the nutrients by bacterial enzymes. The primary non-toxic trans- 

 formation products give rise, by secondary fermentative decomposition, to very 

 toxic transformation products which may become non-toxic as a result of further 

 decomposition. They are not formed in the cell, since autolyzed cells are only 

 slightly toxic and are not regularly produced in the culture when amino acids are 

 present, but are more frequently produced from albumoses and peptones. 



Hemolysin, or the enzyme which "dissolves" red blood cells, is formed by a num- 

 ber of bacteria including B. pyocyaneus, B. tetani, B. coli, staphylococci, and strepto- 

 cocci. This enzyme was first considered to be of the nature of a proteolytic enzyme, 

 but more recent studies have shown these enzymes to be distinctly different. ^ No 

 definite relationship has been established between the hemolytic power of an organism 

 and its pathogenicity. 



The bacteriolytic enzyme of certain bacteria is closely related to the proteolytic 

 and hemolytic enzymes. Pyocyanase, or the bacteriolytic enzyme of B. pyocyaneus, 

 has been studied most extensively. This enzyme or enzyme-like substance is rela- 

 tively thermostabile, resisting heating at 100° C. for thirty minutes. 



Rennet (lab), the enzyme responsible for milk coagulation, is produced abundant- 

 ly by bacteria, such as B. prodigiosus, B. pyocyaneus, B. fluorescens, B. amylobacter, 



' Dernby, K. G.: Biochem. Ztschr., 126, 105. 1921; Dernby, K. G., and Blanc, T-: J- Bad., 6, 

 419. 1921. 



^ Corper, H. J., and Sweany, H. C: /. Biol. Chem., 29, xxi. 1914; J. Bad., 3, 129. 1918. 



3 Jordan, E. O.: Biol. Studies, Pupils of W. T. Sedgwick, p. 124. Boston, 1906. 



'' Dernby, K. G., and Siwa, S.: Biochem. Ztschr., 134, i. 1922. 



5 McNeil, A., and Kahn, B. L.: /. Immitnol., 3, 295. 1918; Orcutt, M. L., and Howe, P. E.: 

 J. Exper. Med., 35, 409. 1922. 



