Phenylalanine and Tyrosine Synthesis 



215 



From the data in Tables I and II two general conclusions 

 may be drawn. (1) Yeast growing on a medium containing 

 glucose as the principal nutrient derives about 15-20 per 



Table I 



Isotope Concentrations of Amino-acids Obtained from Yeast Protein 

 AFTER Incubation with Labelled Acetate 



Yeast grown in the presence of 10 parts of glucose and 1 part of labelled acetate. 



Initial Acetate . 

 Final Acetate 

 Protein . 

 Glutamic Acid . 

 Aspartic Acid 

 Alanine (Ca-(-C)3) 

 Tyrosine . 

 Benzoic Acid* . 

 Serine 

 Glycine . 



*Froni phenylalanine. 



Table II 



Isotope Concentrations of Amino-acids Obtained from Yeast Protein 



AFTER Incubation with Acetate Labelled with ^^C and ^*C 

 Yeast grown in medium containing 10 parts of glucose and 1 part of acetate "CHg^^COOH. 

 RIC is the ratio of the isotope concentration of the acetate and of the compound isolated. 



(countsjmin.) 



Initial acetate 22800 



Final acetate 1270 



Protein 1980 



Fatty acids 7800 



Glutamic acid 3700 



Aspartic acid 730 



Phenylalanine 20 



Tyrosine 19 



Leucine 3300 



Valine 720 



Lysine 6150 



Glycine 100 



"C 

 {Atom % excess) 



10 

 

 

 3 

 1 

 

 

 

 1 

 

 2 

 



•4 



•70 



•91 



•66 



•83 



•25 



•02 



•03 



•27 



•15 



•97 



•06 



RIC "C 

 RIC "C 



100 

 0-83 

 0-99 

 98 

 0-92 

 1-34 



119 

 2 20 

 0-97 

 0-76 



