Evidence for polypeptide synthesis in the caiman from mixtures deficient in essential amino acids
Coulson, R.A.; Herbert, J.D.
Journal of Nutrition 104(11): 1396-1406
1974
ISSN/ISBN: 0022-3166 PMID: 4419682 Document Number: 71127
Caimans were given by injection a complete balanced mixture of free amino acids in the same ratio as that found in fish muscle (complete mix) or mixtures of the same composition and ratio except that 3 essential amino acids were omitted (incomplete mix). The half-life of each amino acid in plasma was estimated and compared with the half-life of the same amino acid when given alone. Whereas there were large differences in half-lives among the amino acids when given singly, every amino acid component of both mixtures disappeared at about the same rate. Essential amino acids in the balanced mixes disappeared several times as fast as they did when given singly. Removal of amino acids from plasma after injection of unbalanced mixes was much slower than that from balanced mixes, and the amino acids disappeared at different rates. The half-lives of single amino acids commonly found in proteins were reduced by subsequent injection of balanced complete or incomplete mixes, while the half-lives of amino acids not found in proteins were unaffected. Inhibition of protein synthesis by cycloheximide lengthened the half-lives of all the amino acids in both the complete and incomplete mixes, and acceleration of protein synthesis by insulin injection shortened the half-lives of amino acids in both mixes. It is postulated that immediate protein synthesis follows injection of complete balanced mixtures, and that some type of macromolecule synthesis follows injection of incomplete mixtures, balanced except for the omission of 3 amino acids.