Phosphorylation of tyrosine aminotransferase in vitro by cyclic nucleotide-dependent protein kinases

An intraperitoneal injection of either leucine (1.57 mg/g body wt) or valine (2 mg/g body wt) into newborn mice led to a rapid accumulation of inactive monoribosomes in their brains. $\text{In}\text{vitro}$ measurements of protein synthesis by the remaining active ribosomes in leucine-treated mice revealed that polypeptide chain elongation was also inhibited. When a mixture of the seven amino acids from the leucine transport system was injected (0.15 mg each amino acid/g body wt) following the valine or leucine treatment, brain monoribosomes did not accumulate and elongation rates in the leucine-treated mice were only slightly altered.