A QUANTITATIVE STUDY OF RECYCLING OF ISOTOPE FROM GLYCINE-1-C14,α-N15 INTO VARIOUS SUBUNITS OF THE URIC ACID MOLECULE IN A NORMAL SUBJECT*

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Abstract
Glycine-1-C14, [alpha]-N15 was administered orally to a control subject, and incorporations of C14 and N15 into individual atoms of uric acid, and into hippuric acid, were followed for 24 days. Glycine-1-C14 labeled C-4 of uric acid almost exclusively. Glycine N15 labeled N-1, N-3, and N-9 appreciably, in addition to its direct incorporation into N-7. The N15 in atoms other than N-7 reached 35 to 40% in 3 weeks. Parallel incorporation of N15 and C14 into N-7 and C-4 of uric acid was observed. Similar analyses of hippuric acid gave no evidence for differential rates of isotopic turnover of [alpha]-N and carboxy-C of glycine. The data indicate that all of the N15 in N-7 of uric acid in this normal subject was accounted for by direct incorporation of the intact glycine molecule; there was no detectable recycling of N15 into N-7 by secondary pathways.