Effects of Dietary Phenylalanine on Activity of Phenylalanine Hydroxylase from Rat Liver. ∗

Abstract

Summary

The activity of phenylalanine hydroxylase from livers of young, male rats fed L-phenylalanine is suppressed by as little as 1% of the amino acid fed for 2 weeks. Larger amounts and a longer period of feeding result in further decreases in measured activities whether animals are pair-fed or fed ad libitum. Growth is depressed also with high levels of phenylalanine in the diet. The lowered activity of the hydroxylase may be attributable, at least partially, to a real suppression of enzyme synthesis.