Biosynthesis of Protein Amino Acids in Plant Tissue Culture II Further Isotope Competition Experiments Using Protein Amino Acids

The behavior of exogenously supplied alanine, proline, glutamine, glutamic acid and aspartic acid in isotope competition experiments using cells of Paul's Scarlet Rose grown in the presence of glucose-U-(14)C was examined at higher concentrations than were used in part I of this series.Each amino acid contributes significantly to protein above a minimum concentration in the culture medium. There is, therefore, no general difference between the behavior of these amino acids and the behavior of the remainder of the protein amino acids in isotope competition experiments.At higher concentrations increasing amounts of carbon from the amino acids in the culture medium was found in other protein amino acids. Using the relative sizes of these contributions metabolic inter-relationships for these amino acids were deduced.