Fructose as a precursor of amino acids in the lactating cow

¹ School of Veterinary Medicine and College of Agriculture, University of California, Davis, California

The biosynthesis of amino acids from fructose and glucose uniformly labeled with C¹⁴ was studied in lactating cows. There were no major differences in the hexoses as precursors of amino acids, the injection of either hexose resulting in the formation of serine and alanine with highest specific activities. Amino acids from whey protein had the same C¹⁴ distribution as casein amino acids. Cystine was synthesized by the cow, but only to a small extent from fructose.