in PROTEINS AND AMINO ACIDS 90 1 



not utilized at all. Cell suspensions of rabbit appendix, rat thymus, mouse spleen 

 and two mouse lymphosarcomas were injected with radiolabeled glutamate or 

 aspartate by Kit (1954). The respiration and the incorporation of labeled carbon 

 into the CO, and into the cellular proteins were measured. The conclusion was 

 reached that the low endogenous concentration of free aspartate in lymphosar- 

 comas could be in part attributed to the high glycolysis of the tumor. Glutamine 

 was readily taken up and metabolized by Yoshida sarcoma cells when injected 

 intraperitoneally into rats bearing this tumor (Roberts et al., 1956). There was a 

 limited permeability of the cells to glutamic acid. Eagle and associates (1956) 

 have studied the growth response of a mouse fibroblast and the human carcinoma 

 cell (HeLa) to L-glutamic acid and L-glutamine. Both of these cells required 

 L-glutamine for survival and growth in tissue culture. Glutamic acid was approxi- 

 mately one tenth as active as glutamine in the HeLa cell and was non-active in the 

 fibroblasts. Further evidence was obtained as to the impermeability of these 

 cells to glutamic acid. 



The occurrence of D-glutamic acid in the proteins of tumor tissues has been 

 given considerable attention for many years (Miller, 1950). Boulanger and 

 Osteux (1954) isolated and purified glutamic acid from hydrolysates prepared by 

 the method of Kogl. No significant differences were observed between the contents 

 of D-glutamic acid in normal and neoplastic tissues. These same investigators also 

 incubated tumor and intestinal homogenates in the presence of pyruvic acid 

 (Boulanger and Osteux, 1953) and a D-amino acid, possibly D-alanine, was found. 

 Muscular, renal and hepatic tumors, however did not produce this acid. D-leucine, 

 according to Vescia et al. (1952), inhibited the hydrolysis of glycyl-L-leucine in 

 normal and in pathological non-neoplastic tissues. In a large number of malignant 

 tumors the D-leucine activated this peptidase activity. 



L-cysteine, selenium cystine and phenyl selenium cysteine were effective in 

 decreasing the incorporation of -''^S-L-cysteine by leukemic leukocytes (Weis- 

 berger et al., 1956). Melchior and Goldkamp (1953) determined the incorporation 

 of ^^S labeled methionine in vitro by the tissues of C3H mice. The mammary 

 tumor had a considerably higher rate of incorporation of methionine than the 

 normal tissues. 



The reactions leading to melanin formation have been established by Fitzpatrick 

 et al. (1950) and Lerner and Fitzpatrick (1950). Markert (1955) also found that 

 tyrosine or its oxidative products were the only substrates used by melanoblasts 

 in the synthesis of melanin. The labeled side chains of tyrosine or dihydroxy- 

 phenylalanine did not serve as melanin precursors as was shown by radioauto- 

 graphs. This finding would cast some doubt upon the accepted scheme for me- 

 lanogenesis. Poppe and Fraedrick (1954) reported a selective uptake of tyrosine- 

 3-''*C in superficial melanotic lesions. Mice bearing Harding-Passey melanoma 

 were injected with single or repeated doses of tyrosine-2-''*C and sacrificed at 

 varying time intervals (Robertson et al., 1955). No significant differences were 

 noted between the normal or malignant tissues in the incorporation of the labeled 

 tyrosine. No differences were found between the normal and melanotic tissues 

 following administration of tyrosine-2-''*C in a patient with malignant melanoma. 



Literature p. gig 



