276 ENZYMES OF BACTERIA 



V. cholerae, etc' It is formed by bacteria on casein-containing and casein-free media, 

 and is readily secreted by the cells into the surrounding medium. At first it was 

 thought to be identical with protease but was later found to be a different enzyme. 



Among the amidases and deaminases, or the enzymes which hydrolyze the amides 

 and amino acids with the formation of ammonia, it is sufficient to mention urease, 

 histozyme, asparaginase, arginase, and purinamidases. Urease is produced by various 

 bacteria in considerable amounts. The formation of the enzyme is greatly influenced 

 by the composition of the substrate. Histozyme hydrolizes hippuric acid into ben- 

 zoic acid and glycocoll and is formed by various fungi and bacteria. 



A detailed review of the various theories of oxidation-reduction is given else- 

 where.^ It is sufficient to call attention here to the occurrence of some of the enzymes 

 of bacteria responsible for such reactions. A typical oxidation-reduction reaction can 



be illustrated as follows: 



R.CHO H._R.CH.OH 

 R.CHO"^0 "R.COOH 



This reaction can also be represented as follows: 



CH3-CHO-fHa=CH3-CH.OH 

 CH3 • CH<^Q^ - H3 = CH3 • COOH 



One molecule is oxidized and the other is reduced. In the foregoing illustration both 

 molecules ("donator" and "acceptor") are the same. The oxidative phase can be 

 considered as one of dehydration and the reducing phase as one of hydration. It is 

 possible, however, that the acceptor and donator of hydrogen are two distinctly 

 different substances, as in the reduction of methylene blue in fresh milk in the presence 

 of formaldehyde; the latter is the hydrogen donator and the methylene blue the 

 acceptor; nitrate may also act as an acceptor and sulphhydryl group (R.SH) as a 

 donator. The process of dehydration is oxidation and the hydration is reduction. 

 The enzyme which is responsible for the splitting off of the carboxyl group is car- 

 boxylase. No atmospheric oxygen is introduced in the oxido-reductase and carboxyl- 

 ase reactions. The same is true of catalase, which brings about the decomposition of 

 H2O2 to water and oxygen. 



According to Bach and Warburg, direct oxidases, which are capable of activating 

 atmospheric oxygen, are to be distinguished from oxido-reductases (perhydridase). 

 Peroxidases, or the enzymes which are active in the presence of peroxides, and 

 zymases, or the enzymes of fermentation, are also included in this group. 



Respiration, consisting in the absorption of oxygen and the liberation of CO2, is 

 replaced under anaerobic conditions by fermentation or intramolecular respiration. 

 Both result in the liberation of energy. An anaerobe can be grown in the presence of 

 oxygen provided the medium has a proper reduction potential.^ 



' Loeb, A.: Centnilhl.f. BakterioL, I, 32, 471. 1902; Gorini, C: ibid., II, 8, 137. 1902; ibid., 24, 

 369, 470. 1915; ibid., 26, 195, 223. 1917; ibid., 55, 240. 1920. 



^ See Schoen, M.: Le Problcme des fcrmcnialions. Paris: Masson et Cie, 1926; Nord, F. F.: 

 Client. Rev., 3, 60. 1926; also chaps, xii, xiv, in this volume. 



^ Quastel, J. H.: Biocheni. ./., 18, 365. 19^4; 19, 304, 660. 1925. 



