Metabolic Interrelationships among Amino Acids Studied with Isotopic Nitrogen.

Abstract

They injected 15N into rats in various forms: as ammonia and as labeled amino acids, each of 15 different amino acids injected separately. They found that 15N was never transferred to lysine, histidine, or threonine. They found that glutamate tended to label the most heavily, except where 15N was administered as an AA that is interconvertable with another. For example, glycine and serine (reversible), phe and tyr (reversible), thr to glycine (non-reversible), and valine and leu/ileu (prob reversible).