The biosynthesis of protein amino acids in plant tissue culture I. Isotope competition experiments using glucose-U-C14 and the protein amino acids.

Abstract

Isotope competition experiments were performed with cell suspensions of Paul''s Scarlet Rose tissue growing exponentially in a defined medium. Nineteen amino acids usually present in protein were studied for their effects on the incorporation of radioactivity from glucose-U-C14 into protein amino acids. Exogenous lysine, histidine, arginine, threonine, methionine, isoleucine, phenylalanine, or tyrosine was used in total preference to the biosynthesized amino acid for protein synthesis. End product inhibition is proposed as the explanation of these effects. Aspara-gine, valine, leucine, serine and glycine caused partial inhibition of the incorporation of C14 from glucose-U-C14 into these protein amino acids. Some features of the studies of these amino acids provide possible explanations of the parital inhibitions. Exogenous aspartic acid, glutamic arid, glutamine, alanine, and probably proline did not affect the radio- activity of the corresponding amino acids. This lack of effect is explained in terms of compartmentation.