3-MERCAPTOPYRUVATE Sulfurtransferase Activity in Brain and Liver in the Mouse (original) (raw)
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In vitro and ex vivo 13C-NMR Spectroscopy Studies of Pyruvate Recycling in Brain
Developmental Neuroscience, 1998
Pyruvate recycling is a well established pathway in the liver, but in the brain, the cellular localization of pyruvate recycling remains controversial and its physiological significance is unknown. In cultured cortical astrocytes, pyruvate formed from [U-13 C]glutamate was shown to re-enter the TCA cycle after conversion to acetyl-CoA, as demonstrated by the labelling patterns in aspartate C-2 and C-3, lactate C-2, and glutamate C-4, which provides evidence for pyruvate recycling in astrocytes. This finding is in agreement with previous studies of astrocytic cultures, in which pyruvate recycling has been described from [U-13 C]glutamine, in the presence of glutamate, and from [U-13 C]aspartate. Pyruvate recycling in brain was studied in fasted rats receiving either an intraperitoneal or a subcutaneous injection of [1,2-13 C]acetate followed by decapitation 30 min later. Extracts of cortical tissue were analysed with 13 C-NMR spectroscopy and total amounts of amino acids quantified by HPLC. Plasma extracts were analysed with 1 Hand 13 C-NMR spectroscopy, and showed a significantly larger amount of [1,2-13 C]acetate in the intraperitoneal group compared to the subcutaneous group. Furthermore, a small amount of label was detected in glucose in both groups. In the subcutaneously injected rats, [4-13 C]glutamate and [2-13 C]GABA were less enriched than plasma glucose, which might have been the precursor. In the intraperitoneally injected rats, however, pyruvate formation from [1,2-13 C]acetate, and re-entry of this pyruvate into the TCA cycle was demonstrated by the presence of greater 13 C enrichment in [4-13 C]glutamate and [4-13 C]glutamine compared to the subcutaneous group, probably resulting from the significantly higher [1,2-13 C]acetate concentration in brain and plasma.
Properties and Localization of the Sulfate-Activating System in Rat Brain
Journal of Neurochemistry, 1987
Abstract: The formation of the sulfate donor [35S]3′-phos-phoadenosine 5′-phosphosulfate (PAPS) from inorganic [35S]sulfate was studied using a novel assay. The assay was based on the quantitative transfer of radioactivity from [35S]PAPS to β-naphthol under the action of phenolsulfo-transferase activity from rat brain cytosol, with the [35S]β-naphthyl sulfate formed being isolated by polystyrene bead c'iromatography. This simple assay was validated by comparison of results with those derived from direct assay of [35S]PAPS isolated by either TLC or ion exchange chroma-tography. [35S]PAPS formation by a high-speed supernatant of rat cerebral cortex occurred with an optimal pH of ∼7.6, varied linearly with time and protein concentration, and depended on the presence of Mg2+-ATP. The latter could not be replaced by other nucleotides such as GTP, UTP, or CTP, which at 1–5 mM concentrations inhibited the reaction. Mg2+ could not be replaced by Mn2+, which at micro-r olar concentrations inhibited the reaction. The apparent Km values of Mg2+-ATP (at 0.1 mM [35S]sulfate) and inorganic sulfate (at 5 mM Mg2+-ATP) were 2.7 and 0.2 mM, respectively. These kinetics parameters corresponded to those reported for purified ATP sulfurylase (EC 2.7.7.4), the enzyme responsible for the first step of PAPS synthesis in liver. The product of its reaction, [35S]adenosine 5′-phos-phosulfate (APS), could not be detected after incubations, an observation implying that the action of APS kinase was not rate limiting in cerebral extracts tested under the selected experimental conditions. [35S]PAPS formation was detectable in cytosolic fractions from various brain regions, which displayed only limited differences in synthesizing activity. Among subcellular fractions from cerebral cortex, [35S]PAPS formation only occurred in the cytosolic fractions, including that derived from hypoosmotically shocked synaptosomes. [35S]PAPS formation was not detectable in the crude cortical homogenate, and this was attributable to a thermolabile inhibitory effect of cerebral membranes toward the cytosolic synthesizing system.
Effect of chronic treatment with some drugs on the enzymatic activities of the rat brain
Biochemical Pharmacology, 1979
AMract-In untreated and treated rats. age-dependent changes of some cerebral enzymatic activities (lactate dehydrog~n~e; citrate synthase and malate dehydrog~nase; total N ADH~yt~rome c reductase and cytochrome oxidase) were studied in the homogenate in tofu and in the crude mit~hon~ial fraction of the brain from the 16th to the 28th week of age. at 4-week intervals. All the activities studied exhibited anatural peak around the 20th week of life. and subsequently they decreased to lower values. The tested drugs (medibazine. trimetazidine. (-'jeburnamonine, papaverine, suloctidil, bamethan. inositol niacinate. and UDP-glucose) were administered daily for periods of 4.8 or I2 weeks each (16-20. 16-24. 16-28 or 24-28 weeks of life) by intraperitoneal route and at one dose level ( 1 or 5 mg/kg). The drugs tested exerted different
Brain metabolism of exogenous pyruvate
Journal of Neurochemistry, 2005
Pyruvate given in large doses may be neuroprotective in stroke, but it is not known to what degree the brain metabolizes pyruvate. Intravenous injection of [3-13 C]pyruvate led to dose-dependent labelling of cerebral metabolites so that at 5 min after injection of 18 mmoles [3-13 C]pyruvate/kg (2 g sodium pyruvate/kg), approximately 20% of brain glutamate and GABA were labelled, as could be detected by 13 C nuclear magnetic resonance spectrometry ex vivo. Pyruvate, 9 mmoles/kg, was equivalent to glucose, 9 mmoles/kg, as a substrate for cerebral tricarboxylic acid (TCA) cycle activity. Inhibition of the glial TCA cycle with fluoroacetate did not affect formation of [4-13 C]glutamate or [2-13 C]GABA from [3-13 C]pyruvate, but reduced formation of [4-13 C]glutamine by 50%, indicating predominantly neuronal metabolism of exogenous pyruvate. Extensive formation of [3-13 C]lactate from [2-13 C]pyruvate demonstrated reversible carboxylation of pyruvate to malate and equilibration with fumarate, presumably in neurones, but anaplerotic formation of TCA cycle intermediates from exogenous pyruvate could not be detected. Too rapid injection of large amounts of pyruvate led to seizure activity, respiratory arrest and death. We conclude that exogenous pyruvate is an excellent energy substrate for neurones in vivo, but that care must be taken to avoid the seizure-inducing effect of pyruvate given in large doses.
Scientific Reports, 2013
Human mercaptolactate-cysteine disulfiduria (MCDU) was first recognized and reported in 1968. Most cases of MCDU are associated with mental retardation, while the pathogenesis remains unknown. To investigate it, we generated homozygous 3-mercaptopyruvate sulfurtransferase (MST: EC 2.8.1.2) knockout (KO) mice using C57BL/6 embryonic stem cells as an animal model. The MST-KO mice showed significantly increased anxiety-like behaviors with an increase in serotonin level in the prefrontal cortex (PFC), but not with abnormal morphological changes in the brain. MCDU can be caused by loss in the functional diversity of MST; first, MST functions as an antioxidant protein. MST possessing 2 redox-sensing molecular switches maintains cellular redox homeostasis. Second, MST can produce H 2 S (or HS 2 ). Third, MST can also produce SO x . It is concluded that behavioral abnormality in MST-KO mice is caused by MST function defects such as an antioxidant insufficiency or a new transducer, H 2 S (or HS 2 ) and/or SO x deficiency.
Journal of Neurochemistry, 2002
Lactate metabolism in the adult rat brain was investigated in relation with the concept of lactate trafficking between astrocytes and neurons. Wistar rats were infused intravenously with a solution containing either [3-13 C]lactate (534 mM) or both glucose (750 mM) and [3-13 C]lactate (534 mM). The time courses of both the concentration and 13 C enrichment of blood glucose and lactate were determined. The data indicated the occurrence of [3-13 C]lactate recycling through liver gluconeogenesis. The yield of glucose labeling was, however, reduced when using the glucose-containing infusate. After a 20-min or 1-h infusion, perchloric acid extracts of the brain tissue were prepared and subsequently analyzed by 13 C-and 1 H-observed/ 13 C-edited NMR spectroscopy. The 13 C labeling of amino acids indicated that [3-13 C]lactate was metabolized in the brain. Based on the alanine C3 enrichment, lactate contribution to brain metabolism amounted to 35% under the most favorable conditions used. By contrast with what happens with [1-13 C]glucose metabolism, no difference in glutamine C2 and C3 labeling was evidenced, indicating that lactate was metabolized in a compartment deprived of pyruvate carboxylase activity. This result confirms, for the first time from an in vivo study, that lactate is more specifically a neuronal substrate. Key Words: 13 C-NMR-Lactate-Brain metabolism-Neurons-Astrocytes.