Premium
High‐Affinity Transport of γ‐Aminobutyric Acid, Glycine, Taurine, L‐Aspartic Acid, and L‐Glutamic Acid in Synaptosomal (P 2 ) Tissue: A Kinetic and Substrate Specificity Analysis
Author(s) -
Debler Edmund A.,
Lajtha Abel
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb05747.x
Subject(s) - glycine , aspartic acid , taurine , glutamic acid , chemistry , biochemistry , aminobutyric acid , glutamate decarboxylase , amino acid , enzyme , receptor
In a cortical P 2 fraction, [ 14 C]γ‐aminobutyric acid ([ 14 C]GABA), [ 14 C]glycine, [ 14 C]taurine, and [ 14 C]glutamic and [ 14 C]aspartic acids are transported by four separate high‐affinity transport systems with L‐glutamic acid and L‐aspartic acid transported by a common system. GABA transport in cortical synaptosomal tissue occurs by one high‐affinity system, with no second, low‐affinity, transport system detectable. Only one high‐affinity system is observed for the transport of aspartic/glutamic acids; as with GABA transport, no low‐affinity transport is detectable. In the uptake of taurine and glycine (cerebral cortex and pons‐me‐dulla‐spinal cord) both high‐ and low‐affinity transport processes could be detected. The high‐affinity GABA and high‐affinity taurine transport classes exhibit some overlap, with the GABA transport system being more specific and having a much higher V max value. High‐affinity GABA transport exhibits no overlap with either the high‐affinity glycine or the high‐affinity aspartic/glutamic acid transport class, and in fact they demonstrate somewhat negative correlations in inhibition profiles. The inhibition profiles of high‐affinity cortical glycine transport and those of high‐affinity cortical taurine and aspartic/glutamic acid transport also show no significant positive relationship. The inhibition profiles of high‐affinity glycine transport in the cerebral cortex and in the pons‐medulla‐spinal cord show a significant positive correlation with each other; however, high‐affinity glycine uptake in the pons‐medulla‐spinal cord is more specific than that in the cerebral cortex. The inhibition profile of high‐affinity taurine transport exhibits a nonsignificant negative correlation with that of the aspartic/glutamic acid transport class.