CARBOHYDRATE ENZYMES 65 



boxy lie acid. Neuberg and Czapski * demonstrated the presence of 

 carboxylase in the juice of top yeast. Bau 2 studied the action of 

 yeast on pyroracemic acid in the presence of certain inorganic salts. 

 No carboxylase could be found, which confirmed Neuberg's theory 

 that this enzyme does not diffuse from living yeast into the surround- 

 ing medium. Later Bau 3 stated that carboxylase could be demon- 

 strated in dried yeast 20 years old. Other enzymes such as invertase, 

 maltase, melibiase, emulsin, amygdalase, lipase and oxidase were 

 found. 



Glucosides: Emulsin: Fischer and Thierfelder have shown that 

 some yeasts are able to split the a-methylglucosides (substances ob- 

 tained from a condensation of methyl alcohol with glucose) into 

 methyl alcohol and glucose. They are not able to split the /3-methyl- 

 glucosides, however. 



According to Fischer, this action is not brought about by a 

 special enzyme, but by maltase which possesses the ability of splitting 

 both the a-methylglucosides and maltose. On the contrary, the 

 /3-methylglucosides are not decomposed except by an emulsin which 

 acts to break up this substance. The investigations of Bresson 4 

 seem to prove, on the contrary, the existence of a special enzyme in 

 the yeasts of Frohberg, which is sharply set apart from sucrase and 

 maltase, and a-methylglucase. 



Whatever is the truth, many yeasts are known which are able to 

 ferment the a-methylglucosides. Some of these are Sch. octosporus, 

 Pombe, mellacei, S. thermantitonum, the yeast of Logos, the yeast 

 of Frohberg, and certain yeasts of Saaz. 



The investigations of Henry and Auld 5 have indicated that when 

 yeast acts on amygdaline in the presence of toluene at 40, after 5 

 days about 33 per cent of the glucoside is decomposed and after 11 

 days, 67 to 70 per cent. From this, these authors are led to believe 

 that an emulsin exists in yeasts. Now it seems that certain yeasts 

 may act upon the /3-methylglucosides which, according to Fischer, 

 are not decomposed by emulsin. 



1 Neuberg, C. and Czapski, L. Carboxylase in the juice of top yeast. Bio- 

 chem. Zeit. 67, 9-11, 1914. Chem. Abstracts, 9 (1915), 472. 



2 Bau, A. Carboxylase. Wochenschr. Brau. 32, 405-6. Chem. Abstracts, 

 11 (1916), 797. 



3 Bau, A. Yeast carboxylase; its permanence in a dry state as compared with 

 the other enzymes of yeast. Biochem. Zeit. 73, 340-368. 



4 Bresson. Sur Texistence d'une methylglucocase specific dans la levure de 

 biere. Comp. Rend. Acad. Sci. 151, 1910. 



6 Henry, A., and Auld, M. On the probable existence of emulsin in yeast. 

 Proc. Roy. Soc. 76, 1905. 



