56 PHYSIOLOGY OF YEASTS 



endotryptase, a proteolytic enzyme which we shall discuss further 

 on in this book. Also derivatives of the albuminoids have been 

 demonstrated such as the amino acids (leucine and tyrosine); these 

 are also products of digestion by the endotryptase. 



Schutzemberger l has demonstrated the purine derivatives (xanthine, 

 hypoxan thine, guanine). Kossel 2 and Buchner 3 have found nucleic 

 acids in rather large quantities. 



As the nucleus of yeasts is usually small and poor in chromatin, 

 Meyer has been led to think that this nucleic acid is not derived entirely 

 from the nucleus but also from the protoplasm. According to this au- 

 thor, the metachromatic corpuscles which are so abundant in yeasts 

 result, as we have said, from a combination of nucleic acids with an un- 

 known organic base. Kohl agrees with this and also states that these 

 bodies represent nucleo-proteins. 



Belohoubek has analyzed yeasts chemically with the following re- 

 sults: 



Composition Fresh Yeast Dry Yeast 



Water 68.02 



Nitrogenous matter. . 13. 10 40. 98 



Fatty matter 0. 90 2. 80 



Cellulose 1.75 5.47 



Starchy material 14. 10 44. 10 



Organic matter 0.34 1.06 



Mineral matter 1 . 77 5. 54 



Miscellaneous 0. 02 0. 05 



Jones 4 has given some attention to the nucleic acids in yeasts. He 

 prepared the potassium salt of guanylic acid from yeast. In another 

 investigation, two dinucleotides were obtained, one yielding guanine 

 and cytosine and the other adenine and uracil. He also described a 

 compound of guanosine and guanylic acid. In studying the struc- 

 ture of yeast nucleic acid, Jones and Read 5 hydrolyzed yeast nucleic 

 acid to yield a dinucleotide which was shown to be adenine-uracil. The 



1 Schutzemberger. Les Fermentations. Paris, 1892. 



2 Kossel. Ueber das Nuclein der Hefe, Zeit. physiol. Chemie, 3. 



3 Buchner, Ed. Alkoholische Garung ohne Hefezellen. Berichte der deutsch. 

 Gesellsch. 30, 1897. 



4 Jones, W. Formation of guanylic acid from yeast nucleic acid. J. Biol. 

 Chem. 12, 31-5. The partial enzymic hydrolysis of yeast nucleic acid. J. Biol. 

 Chem. 17, 71-80. Simpler nucleotides from yeast nucleic acid, J. Biol. Chem. 20, 

 25-35 (1915). 



6 Jones, W., and Read, B. E. Adenin-uracil dinucleotide and the structure 

 of yeast nucleic acid. J. Biol. Chem. 29, 111-22. The mode of nucleotide linkage 

 in yeast nucleic acid. J. Biol, Chem. 29, 123-6. Uracil-cytosine dinucleotide. 

 J. Biol. Chem. 31, 39-45. 



