Journal of neurochemistry 16:549-558.




Studies in vivo and in vitro of the distribution of label in C-1 of glutamate and glutamine and C-4 of aspartate in the free amino acids of brain were carried out. [1-14C]Acetate was used both in vivo and in vitro and L-[U-14C]aspartate and L-[U-14C]glutamate were used in vitro. (1) The results obtained with labelled acetate and aspartate suggest that CO2 and a 3-carbon acid may exchange at different rates on a CO2-fixing enzyme. (2) The apparent cycling times of both glutamate and glutamine show fast components measured in minutes and slow components measured in hours. (3) With [l-14C]acetate in vitro glutamine is more rapidly labelled in C-1 than is glutamate at early time points; the curves cross over at about 7 min. (4) The results support and extend the concept of metabolic compartmentation of amino acid metabolisn1 in brain

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