Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A crude mitochondrial fraction (M) derived from manually disrupted cerebellar tissue and enriched in choline acetyltransferase (ChAT) activity was fractionated by centrifugation in discontinuous and continuous sucrose gradients. Further purification of 'cholinergic' synaptosomes was achieved (relative specific activity (RSA) of ChAT greater than 3), but the overlap with other synaptosomal populations was still considerable. Hand-homogenized cerebella processed through the full fractionation procedure described here and in previous papers yielded preparations enriched in certain neuronal structures and a fraction in which 'heavy' free mitochondria was concentrated. To characterize these preparations the activities of two transmitter enzymes (CHAT and glutamate decarboxylase, GAD) and 6 mitochondrial enzymes (succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), monoamine oxidase, citrate synthase, fumarase and GABA-aminotransferase) were determined. The distribution of the transmitter enzymes was clearly different in the preparations containing various neuronal structures. The GAD:ChAT RSA ratio was 2.4 for the glomerulus particles, 1.3 for the molecular layer fragments, 0.6 for the myelinated axon segments, and 0.2 for the 'cholinergic' synaptosomes. The mitochondrial enzyme profile of the preparations comprising mainly neuronal structures differed markedly from that of the 'free' mitochondrial fraction. Notably the latter was greatly enriched in GDH (RSA 5.6), whereas the SDH:GDH RSA ratio was relatively high in the former preparations. Nevertheless there were notable differences in the enzyme profile of the fractions of predominantly neuronal origin indicating that the enzyme composition of mitochondria of neuronal processes is not uniform.
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PMID:Subcellular fractionation of rat cerebellum: separation of synaptosomal populations and heterogeneity of mitochondria. 21 84

Nonsynaptic mitochondria isolated from rat brain hippocampus were compared with those obtained by means of the same preparative procedure from cerebral cortex and striatum. Protein recovery, marker enzyme activities (lactate dehydrogenase, citrate synthase, and acid phosphatase), state 4 respiration, and response to hypoosmotic shock showed no difference among the three cerebral regions, suggesting homogeneous behavior during the subfractionation procedure. Cholinergic markers--choline acetyltransferase, acetylcholinesterase activities, and high-affinity choline uptake--evaluated on synaptosomes showed the classic regional pattern with an enrichment in the striatum (striatum much greater than hippocampus). The coupling state of the mitochondrial fractions was maintained (respiratory control ratios ranging from 3.62 to 5.08 with glutamate + malate as oxidizable substrates), showing a metabolic competence sufficient to perform metabolic studies. Regional differences were found in state 3, uncoupled state of respiration, and cytochrome oxidase activity. Hippocampus showed the lower values (hippocampus less than striatum less than cortex). A possible role of this lower capacity of mitochondrial energy metabolism in determining the sensitivity of hippocampal neurons to ischemia or epileptic seizures is suggested.
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PMID:Oxidative metabolism of nonsynaptic mitochondria isolated from rat brain hippocampus: a comparative regional study. 283 1

Acyl dithioesters of CoA have been synthesized by transesterification. The alpha-hydrogens have a spectrally determined pKa of 12.5 +/- 0.14. The hydroxide catalyzed enolization rate is estimated to be 600 M-1.s-1. The absorbance of the dithioester, lambda max = 306 nm, can be used to monitor both the condensation and transesterification reactions that use CoA-Ac as a substrate. For citrate synthase at pH 7.4 Vmax = (4.0 +/- 0.4).10(-4) s-1 and Km = 53 +/- 7.5 microM, which are 2.10(-6) and 3.3-times the Vmax and Km values observed for CoAS-Ac, while for Ac-CoA: choline O-acetyltransferase (EC 2.3.1.6) at pH 7.0 Vmax = (1.1 +/- 0.2).10(-2) mumol.s-1.(mg protein)-1 and Km = 83 +/- 33 microM, which are 0.077 and 10-times the values observed with CoAS-Ac, respectively. The CoA dithioesters are stable at low pH, but hydrolyze with a second-order rate constant of 8.2.10(-2) M-1.s-1 at pH 11.4. The spectral properties of these dithioesters should allow these analogs to be used as probes of the structure of enzyme bound intermediates.
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PMID:Coenzyme A dithioesters: synthesis, characterization and reaction with citrate synthase and acetyl-CoA:choline O-acetyltransferase. 333 28

The activities of five enzymes involved in acetyl-CoA synthesis, pyruvate dehydrogenase complex, ATP citrate lyase, carnitine acetyltransferase, acetyl-CoA synthetase, and citrate synthase, were determined in normal nucleus interpeduncularis and nucleus interpeduncularis in which cholinergic terminals were removed following lesion of the habenulointerpeduncular tract. The activities of aspartate transaminase, fumarase, and GABA transaminase also were determined to compare the effect of lesion on other mitochondrial enzymes which are not linked to the biosynthesis of ACh. In normal nucleus interpeduncularis the activities of carnitine acetyltransferase and pyruvate dehydrogenase complex were higher than the activity of ChAT (choline acetyltransferase), whereas the activities of acetyl-CoA synthetase and citrate synthase were considerably lower than that of ChAT. The effect of the lesion separated the enzymes into two groups: the activities of pyruvate dehydrogenase complex, carnitine acetyltransferase, fumarase and aspartate transaminase decreased by 30--40%, whereas the activities of the other enzymes descreased 5--15%. ChAT activity was in all cases less than 15% of normal. It could be concluded that none of the acetyl-CoA synthesizing enzymes decreased to the degree that ChAT did. Only pyruvate dehydrogenase complex and carnitine acetyltransferase seem to be localized in cholinergic terminals to a significant degree. ATP citrate lyase as well as acetyl-CoA synthetase seem to have less significance in supporting acetyl-CoA formation in cholinergic nerve terminals.
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PMID:Acetyl-CoA synthesizing enzymes in cholinergic nerve terminals. 610 88

The activities of ATP-citrate lyase in frog, guinea pig, mouse, rat, and human brain vary from 18 to 30 mu mol/h/g of tissue, being several times higher than choline acetyltransferase activity. Activities of pyruvate dehydrogenase and acetyl coenzyme A synthetase in rat brain are 206 and 18.4 mu mol/h/g of tissue, respectively. Over 70% of the activities of both choline acetyltransferase and ATP-citrate lyase in secondary fractions are found in synaptosomes. Their preferential localization in synaptosomes and synaptoplasm is supported by RSA values above 2. Acetyl CoA synthetase activity is located mainly in whole brain mitochondria (RSA, 2.33) and its activity in synaptoplasm is low (RSA, 0.25). The activities of pyruvate dehydrogenase, citrate synthase, and carnitine acetyltransferase are present mainly in fractions C and Bp. No pyruvate dehydrogenase activity is found in synaptoplasm. Striatum, cerebral cortex, and cerebellum contain similar activities of pyruvate dehydrogenase, citrate synthase, carnitine acetyltransferase, fatty acid synthetase, and acetyl-CoA hydrolase. Activities of acetyl CoA synthetase, choline acetyltransferase and ATP-citrate lyase in cerebellum are about 10 and 4 times lower, respectively, than in other parts of the brain. These data indicate preferential localization of ATP-citrate lyase in cholinergic nerve endings, and indicate that this enzyme is not a rate limiting step in the synthesis of the acetyl moiety of ACh in brain.
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PMID:Regional and subcellular distribution of ATP-citrate lyase and other enzymes of acetyl-CoA metabolism in rat brain. 610 1

The activity of ATP-citrate lyase in homogenates of five selected rat brain regions varied from 2.93 to 6.90 nmol/min/mg of protein in the following order: cerebellum less than hippocampus less than parietal cortex less than striatum less than medulla oblongata and that of the choline acetyltransferase from 0.15 to 2.08 nmol/min/mg of protein in cerebellum less than parietal cortex less than hippocampus = medulla oblongata less than striatum. No substantial differences were found in regional activities of lactate dehydrogenase, pyruvate dehydrogenase, citrate synthase or acetyl-CoA synthase. High values of relative specific activities for both choline acetyltransferase and ATP-citrate lyase were found in synaptosomal and synaptoplasmic fractions from regions with a high content of cholinergic nerve endings. There are significant correlations between these two enzyme activities in general cytocol (S3), synaptosomal (B) and synaptoplasmic (Bs) fractions from the different regions (r = 0.92-0.99). These data indicate that activity of ATP-citrate lyase in cholinergic neurons is several times higher than that present in glial and noncholinergic neuronal cells.
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PMID:ATP citrate lyase in cholinergic nerve endings. 612 37

The activities of choline acetyltransferase and ATP-citrate lyase were significantly correlated (r = 0.995) in fractions of small and large synaptosomes isolated from rat hippocampus and cerebellum. The activities of these two enzymes did not correlate with those of pyruvate dehydrogenase, carnitine acetyltransferase, citrate synthase, acetyl-CoA synthetase, lactate dehydrogenase, or with the rate of high-affinity glutamate uptake in the synaptosomal fractions. The results provide additional evidence linking ATP-citrate lyase to the cholinergic system in the brain.
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PMID:ATP-citrate lyase and other enzymes of acetyl-CoA metabolism in fractions of small and large synaptosomes from rat brain hippocampus and cerebellum. 613 19

Dibutyryl cyclic AMP and butyrate inhibited growth of S-20 (cholinergic) and NIE-115 (adrenergic) neuroblastoma clones. Both these drugs resulted in a parallel increase of choline acetyltransferase and ATP-citrate lyase activities in S-20 neuroblastoma cells. On the other hand, the increase in tyrosine hydroxylase activity in NIE-115 caused by these drugs was not accompanied by a significant change in ATP-citrate lyase activity. Both dibutyryl cyclic AMP and butyrate caused a decrease in fatty acid synthetase activity in both cell lines. The activities of pyruvate dehydrogenase, citrate synthase, choline acetyltransferase, and lactate dehydrogenase in both S-20 and NIE-115 cells were not significantly influenced by the drugs. ATP-citrate lyases from S-20 and NIE-115 had similar kinetic and immunological properties, and their subunits had the same molecular weight as the rat liver enzyme. These data indicate that the differential regulation of ATP-citrate lyase activity in cholinergic and adrenergic cells does not result from the existence of different molecular forms of the enzyme in these cell lines. They also provide further evidence to support the hypothesis that ATP-citrate lyase activity increases during maturation of normal cholinergic neurons and decreases in noncholinergic cells of the brain.
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PMID:The enzymes of acetyl-CoA metabolism in differentiating cholinergic (s-20) and noncholinergic (NIE-115) neuroblastoma cells. 630 53

The activities of pyruvate dehydrogenase, citrate synthase, and choline acetyltransferase in rat brain synaptosomes increased during ontogenesis by 3 and 14 times, respectively. Activity of ATP-citrate lyase decreased by 26% during the same period. Pyruvate consumption by synaptosomes from 1-day-old animals was 40% lower than that found in older rats; however, citrate efflux from intrasynaptosomal mitochondria in immature synaptosomes was over twice as high as that in mature ones. The rates on production of synaptoplasmic acetyl-CoA by ATP-citrate lyase were 1.03, 1.40, and 0.49 nmol/min/mg protein in 1-, 10-day-old, and adult rats, respectively. 3-Bromopyruvate (0.5 mM) inhibited pyruvate consumption by 70% and caused a complete block of citrate utilization by citrate lyase in every age group. Parameters of citrate metabolism in cerebellar synaptosomes were the same as those in cerebral ones. These data indicate that production of acetyl-CoA from citrate in synaptoplasm may be regulated either by adaptative, age-dependent changes in permeability and carrier capacity of the mitochondrial membrane or by the inhibition of synthesis of intramitochondrial acetyl-CoA. ATP-citrate lyase activity is not a rate-limiting factor in this process. Metabolic fluxes of pyruvate to cytoplasmic citrate and acetyl-CoA are presumably the same in both cholinergic and noncholinergic nerve endings. The significance of citrate release from intrasynaptosomal mitochondria as a regulatory step in acetylcholine synthesis is discussed.
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PMID:The contribution of citrate to the synthesis of acetyl units in synaptosomes of developing rat brain. 706 46

Electrolytic lesions made in the medial septum of the rat brain caused an 80% decrease in the activity of choline acetyltransferase and a 33% reduction in ATP-citrate lyase activity in the synaptosomal fraction from the hippocampus. Decreases in the activities of the two enzymes in the cytosol (S3) fraction were 70 and 13%, respectively. The activities of pyruvate dehydrogenase, citrate synthase, acetyl-CoA synthase, and carnitine acetyltransferase in crude hippocampal homogenates and in subcellular fractions were not affected by septal lesions. The data indicate that ATP-citrate lyase is linked to the septal-hippocampal pathway and that the enzyme is preferentially located in cholinergic nerve endings that terminate within the hippocampus.
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PMID:Effects of septal lesions on enzymes of acetyl-CoA metabolism in the cholinergic system of the rat hippocampus. 708 27


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