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Phosphate activated glutaminase is a key enzyme in glutamate synthesis. Here we have employed a quantitative and high-resolution immunogold procedure to analyse the cellular and subcellular expression of this enzyme in the cerebellar cortex. Three main issues were addressed. First, is phosphate activated glutaminase exclusively or predominantly a(More)
Two pools of phosphate-activated glutaminase (PAG) were separated from pig and rat renal mitochondria. The partition of enzyme activity corresponded with that of the immunoreactivity and also with the postembedding immunogold labeling of PAG, which was associated partly with the inner membrane and partly with the matrix. The outer membrane was not labeled.(More)
The cellular concentration of phosphate, the main activator of phosphate activated glutaminase (PAG) is rather constant in brain and kidney. The enzyme activity, however, is modulated by a variety of compounds affecting the binding of phosphate, such as glutamate, calcium, certain long chain fatty acids, fatty acyl CoA derivatives, members of the(More)
[3H]inositol(1,4,5)-trisphosphate (IP3) binding studies have shown decreased [3H]IP3 binding to brain tissue in several neurodegenerative diseases, including Alzheimer's and Huntington's diseases. In addition, previous results obtained from brains of Alzheimer patients indicated a reduction of IP3-receptor protein correlated to neuronal loss. The neurotoxic(More)
Phosphate-activated glutaminase in intact pig renal mitochondria was inhibited 50-70% by the sulfhydryl reagents mersalyl and N-ethylmaleimide (0.3-1.0 mM), when assayed at pH 7.4 in the presence of no or low phosphate (10 mM) and glutamine (2 mM). However, sulfhydryl reagents added to intact mitochondria did not inhibit the SH-enzyme beta-hydroxybutyrate(More)
When rat brain synaptic and non-synaptic mitochondria were incubated with [14C]glutamine, [14C]glutamate was rapidly released to the incubation medium, and the release was stimulated by phosphate, whereas [14C]glutamate accumulated very slowly in the mitochondria and independently of the addition of phosphate. The specific activity of [14C]glutamate(More)
Gln is transported into rat brain synaptic and non-synaptic mitochondria by a protein catalyzed process. The uptake is significantly higher in synaptic than in non-synaptic mitochondria. The transport is inhibited by the amino acids Glu, Asn and Asp, and by the TCA cycle intermediates succinate, malate and 2-OG. The inhibition by 2-OG is counteracted by AOA(More)
The effects of mitochondrial swelling and calcium have been used to study the possible function of the glutamine transporter in regulating glutamine hydrolysis. Salt-induced swelling of pig renal mitochondria and an iso-osmotic mixed salt solution and swelling caused by reducing the osmolarity of the incubation medium, are accompanied by activation of(More)
The kinetics and other properties of phosphate-activated glutaminase have for the first time been studied in the crude mitochondrial fraction (P2 fraction) from human brain. The enzyme is for unexplained reasons inactivated postmortem. The enzyme activity decreases by storing the tissue or homogenate at 37 degrees C. The inactivation is not caused by(More)
Glutamate has been implicated in signal transmission between sensory hair cells and afferent fibers in the inner ear. However, the mechanisms responsible for glutamate replenishment in these cells are not known. Here we provide evidence that phosphate activated glutaminase, which is thought to be the predominant glutamate-synthesizing enzyme in the brain,(More)