Hemoglobin Synthesis from Glycine Labeled with Radioactive Carbon in Its (u-carbon Atom*

Important progress in our knowledge concerning the biological precursors of hemin was made when Bloch and Rittenberg (1) presented evidence that significant amounts of deuterium are incorporated into the hemin of rats fed deuterioacetic acid. Further advances in this field were made by Shemin and Rittenberg (2-4), who showed that glycine labeled with N15 is utilized as a nitrogenous precursor of hemin, whereas other possible amino acids, such as glutamic acid, proline, and leucine, do not act in a similar fashion and contribute only in an indirect way to hemin N by enriching the N15 concentration of the body. It has been reported recently that hemin synthesis from glycine occurs in vitro in the presence of avian blood (5) and with blood from patients with sickle cell anemia (6). It is of considerable interest for an understanding of the mechanism of hemin synthesis to determine whether the a-carbon atom of glycine is also incorporated in hemin. Experiments demonstrating the participation of the a-carbon atom of glycine in the synthesis of hen& are reported in this paper. A preliminary report has been published elsewhere (7).