jQis] Joseph Samuel Hepburn 149 



low temp. is possessed by various enzymes, including those produc- 

 ing hydrolysis of fats, carbohydrates, and proteins; those con- 

 cerned in biochemical oxidations and reductions; the clotting en- 

 zymes; and that of alcoholic fermentation. The enzymes retain 

 their catalytic power after exposure, either in situ or in Solution 

 in vitro, to temp. varying from a few degrees above 0° C. to the 

 temp. of liquid air ( — 180 to — 191° C). The shortest periods 

 of holding — invariably less than i day and usually less than i hr. — 

 were at the temp. of liquid air. The longest period of holding was 

 89 mo. at a temp of —9.4° to — 12.2° C. 



The activity of certain of these enzymes, including rennin, zy- 

 mase, and those hydrolyzing fats, carbohydrates and proteins, has 

 been studied at low temp., varying from that of an ice box to one 

 of — 9° to — 12° C. While the enzymes induce autolytic diges- 

 tion, or act on artificial media, at these temp., the velocities of their 

 reactions are always diminished to a considerable degree. 



BIBLIOGRAPHY 



1. Kastle and Loevenhart: Amer. Chem. Journ., 1900, xxiv, p. 



491. 



2. Pennington and Hepburn : Jottrn. Amer. Chem. See., 1912, 



xxxiv, p. 210; U. S. Dep't of Agri., Bur. of Chem., Circular 75, 

 1911. 



3. Pennington and Robertson: U. S. Dep't of Agri., Bureau of 



Chem., Circular 104, 1912. 



4. KovcHOFF : Ber. d. deutsch, botan. Gesellschaft, 1907, xxv, p. 473. 



5. PozERSKi : Campt, rend. de la soc. de hiol., 1900, lii, p. 714. 



6. Chanoz and Doyon : Campt, rend: de la sac. de hiol., 1900, lii, 



P- 453. 



7. Buchner: Die Zymasegährung. München und Berlin. Druck 



und Verlag von R. Oldenbourg, 1903, pp. 67, 226. 



8. Ahrens: Zeitschr^ f. angewandte Chem., 1900, 483. 



9. Macfadyen: Proc. Royal Soc. af London, 1900, Ixvi, p. 180; 



Lancet, 1900, Ixxviii (i), p. 849. 

 IG. Pennington, Hepburn, St. John, Witmer, Stafford and 



Burrell: Journ. Biol. Chem., 1913, xvi, p. 331. 

 II. Hepburn: U. S. Dep't of Agri., Bureau of Chem., Circular 103, 



1912, p. 6. 



