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COMPARATIVE STUDIES ON THE DEGRADATION OF GABA and TAURINE IN THE BRAIN
Authors:P. Lä  hdesmä  ki, K. Korhonen
Affiliation:Department of Biochemistry, University of Oulu, Oulu, Finland
Abstract:Abstract— The degradation of taurine and GABA in mammalian brain was studied in vivo and in vitro. Small amounts of [35S]isethionate (10–20 pmol/g brain wet weight) and [35S]sulphate (about 2 pmol/g) were detected in mouse brain after intramuscular injection of [35S]taurine. Taurine also produced isethionate in rat brain homogenates (about 20 nmol/h/g protein) and subcellular fractions (about 40 nmol/h/g protein in synaptosomes and about 300 nmol/h/g in mitochondria), but the reaction was not stimulated either by external electrical pulses or by the addition of various cofactors (NAD and NADP in both oxidized and reduced forms, riboflavin, glutathione. pyridoxal-5'-phosphate, ATP) to the incubation medium. [14C]GABA was readily metabolized to [14C]succinate both in vivo and in vitro. Isethionate formation activity was concentrated in the mitochondrial fraction, as was also GABA-T activity. Partially purified GABA-T from calf brain also slightly catalysed the formation of [35S]isethionate (about 1.3 μmol/min/g protein) from [35S]taurine. It appears that the slight formation of isethionate from taurine is coupled to GABA-T activity. The formation of isethionate from taurine is so small, that it apparently has no role in the control of the brain taurine pool.
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