Isolation of a Peptide in Guinea Pig Liver Homogenate and Its Turnover of Leucine

Leucine was synthesized with C14 in the carboxyl group. 10 mg. of the radioactive amino acid (DL) and 0.66 gm. (wet weight) of guinea pig liver homogenate were added to a reaction mixture containing 1.3 per cent of an amino acid mixture corresponding to the composition of casein and 0.005 M fumarate, all in a final volume of 4 ml. of isotonic saline solution(1) at pH 7.4. The reaction was carried out under oxygen for 6 hours at 38°.