UPTAKE AND METABOLISM OF DELTA(1)-PIPERIDINE-2-CARBOXYLIC ACID BY SYNAPTOSOMES FROM RAT CEREBRAL-CORTEX

Delta(1)-Piperidine-2-carboxylic acid (P2C), an intermediate of the L- lysine metabolic pathway in the brain, was studied for its uptake and metabolism in the synaptosome of the rat cerebral cortex. The results of this study showed that the uptake of P2C into the synaptosome was N A(+)-and temperature-dependent with a two-tier transport kinetic (K-m = 2.6 and 0.7 mu M; V-max = 1.6 and 0.73 pmol/min/mg). P2C uptake was only moderately inhibited (approximate to 20%) by L-lysine and its met abolites, L-pipecolic acid and L-alpha-aminoadipic acid at up to 100 m u M, and the putative amino acid neurotransmitters, gamma-aminobutyric acid, L-glutamic acid and L-aspartic acid (25-31%) at 5-500 mu M. The synaptosomal preparation only has a very low activity for metabolizin g P2C to its product L-pipecolic acid. The metabolic activity for P2C was mainly contained in the 27000 X g supernatant S-2 fraction. Since P2C is the precursor of the putative neuromodulator L-pipecolic acid, the understanding of its uptake and metabolic characteristics in the b rain should be of significance.