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Nutritional and 

 genetic approaches 



Nutritional approaches 



We may illustrate the nutritional approach by reviewing the 

 observations of the effect of deficiency of vitamin B 6 on amino 

 acid transport. Ehrlich ascites tumor cells grown in B G -deficient 

 mice are subnormal in accumulating glycine at high loads; added 

 pyridoxal stimulates such deficient cells more strongly than it does 

 ordinary Ehrlich cells (Christensen et al., 1954). The model amino 

 acid, a-aminoisobutyric acid, is concentrated much more weakly 

 by many tissues (except liver) of the intact B 6 -deficient rat than 

 by tissues of well-nourished rats (Riggs and Walker, 1958). Rats 

 receiving 4-deoxypyridoxine (Jacobs and Hillman, 1958; 1960) or 

 penicillamine (Akedo et al., 1960) show deficient intestinal transport 

 of amino acids, corrected by pyridoxal phosphate supplementation. 

 Adding the coenzyme to the perfused intestine eliminates the in- 

 hibiting action of 2,4-dinitrophenol on amino acid transport (Ueda 

 et al., 1960). 



These observations have been particularly interesting because 

 pyridoxal, or its phosphate, is able to take hold of amino acids by 

 Schiff-base formation at the amino group, in a manner that could 

 perhaps satisfy the requirements for the behavior of the carrier or 



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