Effect of different amino acid diets on δ5, δ6 and δ9 desaturases

A high-protein diet with 45% calories from casein increased δ6 desaturase activity in rat-liver microsomes. High-protein diets with 45% calories from a synthetic mixture of amino acids in the same proportion as casein decreased the δ9 desaturase, slightly increased the δ5 desaturase and greatly increased δ6 desaturase activities compared with a high-carbohydrate diet. The elimination of phenylalanine and tyrosine from the synthetic mixtures of amino acids increased the δ6 desaturase activity. Massive amounts of phenylalanine or tyrosine in the diet inhibited δ6 desaturase activity. Tyrosine and phenylalanine may, by conversion to tyrosine, decrease the activity of the δ6 desaturase.