Resolution and Brain Regional Distribution of Cysteine Sulfinate Decarboxylase Isoenzymes from Hog Brain

Abstract

Cysteine sulfinate decarboxylase (CSD; EC 4.1.1.29) activity from porcine brain was resolved into three peaks by hydroxylapatite chromatography. The first two peaks (I and II) did not decarboxylate and were not inhibited by glutamate. The third peak (III) cochromatographed with glutamate decarboxylase (GAD; EC 4.1.1.15) activity. The Km values of cysteine sulfinate for peaks I, II, and III were 5.5 × 10−4m, 1.3 × 10−4m, and 4.5 × 10−3m, respectively. The possibility that the same enzyme was responsible for peak III CSD and GAD activities was suggested by several findings: (1) Mutual competitive inhibition was observed between glutamate and cysteine sulfinate for these activities. (2) Similar first‐order heat‐inactivation curves were obtained for peak III CSD and GAD when incubated at 55xBOC. (3) Both activities were inhibited similarily by ATP and chloride ion. High concentrations of glutamate (0. l m) inhibited peak III CSD activity more than 90% but had no effect on either peak I or II CSD activities. This difference in sensitivity of the isoenzymes to inhibition by glutamate was used to examine the relative regional distributions and the relative contributions to total activity of the glutamate‐sensitive (peak III CSD, GAD) and glutamate‐insensitive (peaks I and II CSD) isoenzymes. Glutamate‐insensitive CSD activity contributed only part of the total activity in all brain regions tested (ranging from 23% in the superior colliculus to 64% in the pons). However, the specific activity of glutamate‐insensitive CSD was more constant than the total or glutamate‐sensitive specific activities among the brain regions tested. The results indicate that GAD is responsible for a significant proportion of the total CSD activity in porcine brain.

Activation of β‐Adrenergic Receptors Stimulates Release of an Inhibitory Transmitter from Astrocytes

“…The experiments described in this report demonstrate that (a) P-receptor activation in primary cultures of astrocytes results in taurine release and (b) receptor-mediated taurine release occurs via a cyclic AMP-dependent intracellular pathway. Taurine may function in the CNS as a neuromodulator or transmitter (Wheler ct al.. 1979: Korpi et al, 1981Oja et al, 1981;Salceda and Pasantes-Modes, 1982;Spears and Martin, 1982) and is an anticonvulsant in laboratory animals and humans (van Gelder, 1978;Arzate. 1981: Fariello et al, 1982;Pasantes-Morales et al, 1982;Oja et al, 1983).…”

Taurine infused intrastriatally elevates, but intranigrally decreases striatal extracellular dopamine concentration in anaesthetised rats

“…High concentrations of taurine and cysteine sulphonic acid decarboxylase, a major synthetic enzyme for taurine, have been found in the striatum and the substantia nigra (Dray and Straughan, 1976;Lombardini, 1976;Spears and Martin, 1982;Tossman et al, 1986;Farrant and Webster, 1989;Palkovits et al, 1990). A high affinity uptake system has been described to accumulate 3(H)-taurine in the striatum (Clarke et al, 1983) as well as in the substantia nigra (Della Corte et al, 1987, 1990.…”

Locally infused taurine, GABA and homotaurine alter differently the striatal extracellular concentrations of dopamine and its metabolites in rats

“…So far a definitive demonstration of the presence of high affinity sodium-independent binding sites for taurine is lacking (Huxtable, 1989). Taurine and its synthetic enzyme, cysteine sulphonic acid decarboxylase, are found in high concentration in the striatum and in the substantia nigra (Lombardini, 1976;Spears and Martin, 1982;Tossman et al, 1986). At least a portion of striatal taurine is associated with neurons destroyed by kainic acid (Nicklas et al, 1979).…”