The specific radioactivity of urinary hippurate glycine was determined after injecting guinea pigs with benzoate and either dl-[2-14C]glutamate or dl-[5-14C]glutamate. The isotope dilution factor for the formation of [14C]glycine was significantly greater (30%) with C-2 labelled glutamate. With either form of labelled glutamate the hippurate glycine was largely carboxyl-group labelled. The observations suggest a route for the incorporation of glutamate carbon into glycine that involves C-5 but not C-2. A hypothesis for glycine biosynthesis from l-glutamate is advanced, consistent with these findings, that includes conversion of l-glutamate to 4-hydroxy-2-oxoglutarate, the scission of the latter to glyoxylate and pyruvate, and the formation of glycine by transamination.
A difference in the incorporation of 14C into hippurate glycine from dl-[2-14C]glutamate and dl-[5-14C]glutamate in guinea pigs
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Kathleen V. Rowsell, Tahsin A. J. Ali, Edward V. Rowsell; A difference in the incorporation of 14C into hippurate glycine from dl-[2-14C]glutamate and dl-[5-14C]glutamate in guinea pigs. Biochem J 15 November 1975; 152 (2): 357–363. doi: https://doi.org/10.1042/bj1520357
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