The Use of Isotopes in the Study of Intermediary Metabolism

Aspects of the metabolism of glycine and of porphyrins. The second Hopkins Memorial Lecture

“…Alanine may be considered to be a member of both groups, since pyruvic acid, its precursor, is formed in glycolysis and is also closely related to acetyl-CoA and oxaloacetate, substances which participate in the tricarboxylic acid cycle. It is of interest to note that the daily rate ofalanine or pyruvate formation in the rat amounts to about 38 m-moles/100 g. (Arnstein & Grant, 1957), compared with 3-5 m-moles/100 g./ day for serine, and, whilst the absolute figures are not very reliable, it is clear that the amounts of alanine, and probably those of the carbon skeletons of glutamic acid and aspartic acid, synthesized daily are about ten times those of serine and glycine.…”