Abstract
Abstract
Three experiments were conducted to investigate the effects of various levels of dietary phenylalanine (Phe) and tyrosine (Tyr) on weight gain, feed conversion, serum Tyr and Phe, and hepatic Phe hydroxylase and Phe-pyruvate transaminase activities in Sprague-Dawley rats. In general, the results indicated that these animals were not able to obtain Tyr from dietary Phe with 100% efficiency when the animals were fed diets devoid of Tyr. At or above the calculated requirement level of Phe (0.8% and greater), this phenomenon might be explained by substrate inhibition of Phe hydroxylase. Serum Tyr appeared to be a better indicator of the amount of dietary Phe and Tyr consumed than was serum Phe.
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