Regulatory Influences on the Production of Gamma-Aminobutyric Acid by a Marine Pseudomonad
AUTOR(ES)
Mountfort, Douglas O.
RESUMO
A pseudomonad capable of producing γ-aminobutyric acid (GABA) was isolated from seawater via an enrichment in which glutamate was the sole carbon and nitrogen source. The organism grew optimally at pH 7.3 and at 25°C. Putrescine, alanine, and glucose-nitrate also served as effective growth substrates. The isolate grew poorly on GABA. Cell suspensions of the organism in 0.02 M phosphate buffer (pH 7.6) containing NaCl (19.4 g liter-1) and MgCl2. 6H2O(3 g liter-1) produced GABA from succinic semialdehyde in combination with glutamate or alanine but not from any substrate alone. Little or no GABA was produced with putrescine or glucose-nitrate as substrates. GABA production in the amino acid cosubstrate systems was transitory with optimum levels occurring in the suspension fluid after 3 h of incubation (0.3 and 0.03 mM for glutamate and alanine cosubstrates, respectively). However, yields of GABA in the cell suspension fluid were low, and quantities near that predicted from stoichiometry could be obtained only by extracting cell suspensions with methanol. GABA release in the suspension fluid was increased with higher pH or by decreasing NaCl. Substitution of the salt by the equivalent Tris-HCl or KCl likewise resulted in increased GABA release. When nigericin (10 μg ml-1) was added to cell suspensions in which NaCl was not decreased, GABA release increased in a way similar to that observed in suspensions with decreased NaCl. The ionophore also decreased GABA uptake by cell suspensions of GABA-grown cells, and the effect was duplicated by lowering NaCl in cell suspensions. The results indicate a role for an Na+-dependent transport system in GABA release.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=195198Documentos Relacionados
- Stimulation of benzodiazepine receptor binding by gamma-aminobutyric acid.
- The gamma-aminobutyric acid system in rabbit cerebellum.
- The third gamma subunit of the gamma-aminobutyric acid type A receptor family.
- Co-release of acetylcholine and gamma-aminobutyric acid by a retinal neuron.
- gamma-Aminobutyric acid stimulates ethylene biosynthesis in sunflower.