title: A difference in the incorporation of 14C into hippurate glycine from DL-(2-14C)-glutamate and DL-(5-14C)glutamate in guinea pigs.
abstract: The specific radioactivity of urinary hippurate glycine was determined after injecting guinea pigs with benzoate and either dl-[2-(14)C]glutamate or dl-[5-(14)C]glutamate. The isotope dilution factor for the formation of [(14)C]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.
mesh_terms: D000596:Amino Acids / Q000302:isolation & purification; D000818:Animals; D001565:Benzoates / Q000378:metabolism; D002250:Carbon Radioisotopes; D005971:Glutamates / Q000378:metabolism*; D005998:Glycine / Q000096:biosynthesis* / Q000652:urine; D006038:Glyoxylates / Q000378:metabolism; D006168:Guinea Pigs; D006626:Hippurates / Q000096:biosynthesis* / Q000652:urine; D007656:Ketoglutaric Acids / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013386:Succinates / Q000032:analysis
chemical_list: D000596:Amino Acids; D001565:Benzoates; D002250:Carbon Radioisotopes; D005971:Glutamates; D006038:Glyoxylates; D006626:Hippurates; D007656:Ketoglutaric Acids; D011773:Pyruvates; D013386:Succinates; D005998:Glycine