70 ENZYMES OR SOLUBLE FERMENTS. 



Torula ureae 1 . Normally urine is free from these organisms and may 

 be kept in the excised bladder for an indefinite period without exhibit- 

 ing any tendency to become alkaline 2 ; in certain abnormal conditions 

 it may undergo an active alkaline fermentation while still in the 

 bladder. The part played by the organisms was for a long time 

 regarded as similar to that of yeast-cells in promoting alcoholic 

 fermentation. Soon however evidence was adduced which showed 

 that the change was not necessarily due solely to the life and growth 

 of the organisms in the solution, for it was found that the fermentation 

 might be very complete in presence of an amount of carbolic acid which 

 is fatal to the development of micro-organisms 3 . The probable existence 

 of an enzyme as a possible factor in the whole process which was thus 

 demonstrated was reduced to a certainty by the experiments of Muscu- 

 lus 4 . Employing the thick mucous excretion of urinary catarrh he 

 precipitated the mucin with alcohol, dried the precipitate at a low 

 temperature, extracted it with water and found the extract to possess 

 active hydrolytic powers in a solution of urea. The proof of the 

 existence of the enzyme in a pathological mucous urine in which there 

 is frequently no reason to suspect the existence of any micro-organisms 

 still left open the question of the isolation of the enzyme from the 

 micro-organism itself. When urine which by exposure to the air 

 has entered into active alkaline fermentation and, as shown by micro- 

 scopic examination, is full of Torulae, is efficiently filtered no enzyme 

 capable of hydrolising urea can be precipitated by alcohol from the 

 clear filtrate. If on the other hand the unfiltered urine be precipitated 

 with an excess of alcohol and the precipitate washed with alcohol and 

 dried in the air, a powder is obtained which is itself extraordinarily 

 active and yields to an aqueous extract a soluble enzyme which rapidly 

 converts urea into ammonia and carbonic acid. The rapidity of the 

 conversion precludes the intervention of any developing organism, and 

 that the change is truly due to an enzyme is shown by the fact that it 

 takes place with equal readiness in presence of chloroform 5 . 



It is of some interest to notice here that from what has been said above the 

 organisms to whose activity the fermentation is due do not discharge their enzyme 



1 Mtiller, Jn. f. prakt. Chem. Bd. LXXXI. (1860), S. 467. Pasteur, Compt. Rend. 

 T. L. 1860, p. 869. van Tieghem, Ibid. T. LVIII. 1864, p. 210. But see also Jaksch, 

 Zt. f. physiol. Chem. Bd. v. (1881), S. 395. Leube, Virchow's Arch. Bd. c. (1885), 

 S. 540. Miquel, Bull, de la Soc. Chim. T. xxix. (1878), p. 387 ; xxxi. p. 391; xxxn. 

 (1879), p. 126. 



2 Cazeneuve et Livon, Compt. Rend. T. LXXXV. (1877), p. 571. Bull, de la Soc. 

 Chim. T. xxvin. (1877), p. 484. ' 



3 Hoppe-Seyler, Med.-chem. Untersuch. Hft. 4, 1871, S. 570. 



4 Compt. Rend. T. LXXVIII. (1874), p. 132; LXXXII. (1876), p. 334. Pfluger's 

 Arch. Bd. xn. (1876), S. 214. See also Lailler, Compt. Rend. T. LXXVIII. p. 361. 



6 Lea, Jl. of Physiol. Vol. vi. (1885), p. 136. 



