BIOSYNTHESIS OF PHENYLALANINE AND TYROSINE IN YOUNG WHEAT AND BUCKWHEAT PLANTS

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Abstract
Several C14-labelled compounds were fed to shoots excised from young plants of Triticum vulgare Vill. or Fagopyrum tataricum (L.) Gaertn. The free and bound phenylalanine and tyrosine were isolated after a metabolic period of 6 hours and their C14content measured. Shikimic acid was superior to glucose and acetate as a precursor of both phenylalanine and tyrosine. Phenyllactic acid and phenylpyruvic acid were easily converted to free phenylalanine and were incorporated into bound phenylalanine as readily as was free phenylalanine itself. Similarly, p-hydroxyphenyllactic acid and p-hydroxyphenylpyruvic acid were converted preferentially to tyrosine. There was some conversion of phenyl compounds to p-hydroxyphenyl compounds but little evidence of the reverse reaction. Radioactive carbon fed as cinnamic, dihydrocinnamic, or p-coumaric acids was not incorporated into either phenylalanine or tyrosine.