Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biological significance of glycogen accumulation and how the process is regulated in Chlamydia trachomatis remains poorly defined. C. trachomatis-infected HeLa cells were cultured in medium containing various glucose concentrations (0, 0.1, 1 or 10 mg ml-1) or in the presence of gluconeogenic carbon sources (20 mM glutamate, 20 mM malate, 20 mM alpha-ketoglutarate or 20 mM oxaloacetate), and the effects of these different culture conditions on the production of infectious chlamydial elementary bodies and glycogen accumulation were monitored. When chlamydiae were cultured in glucose concentrations greater than 1 mg ml-1, optimal growth and maximal glycogen accumulation occurred. In contrast to uninfected HeLa cells, which increased their glycogen stores when grown in the presence of high glucose concentrations, chlamydial glycogen accumulation remained essentially constant. When cultured in medium supplemented with either reduced glucose concentrations or any of the gluconeogenic carbon sources, chlamydiae still grew; however, the yield of elementary bodies was substantially decreased, and there was no significant amount of glycogen accumulated by host HeLa cells or C. trachomatis. This suggests that glycogen accumulation may not be essential for chlamydial survival. Reverse transcriptase-polymerase chain reaction (RT-PCR) results indicated that, despite the fact that the source and amount of carbon available in the medium affected chlamydial glycogen accumulation, the expression of genes required for glycogen metabolism was not significantly changed. Similarly, the expression of several genes encoding key enzymes of central metabolism was not affected by alterations in carbon source or availability. Taken together, the data suggest that, unlike most free-living bacteria, chlamydia are unable to alter the expression of genes involved in carbon metabolism in response to changes in environmental conditions.
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PMID:Regulation of carbon metabolism in Chlamydia trachomatis. 1102 87

Neurons are known to express a high-affinity Na+ -coupled dicarboxylate transporter(s) for uptake of tricarboxylic acid cycle intermediates, such as alpha-ketoglutarate and malate, which are precursors for neurotransmitters including glutamate and gamma-aminobutyric acid. There is, however, little information available on the molecular identity of the transporters responsible for this uptake process in neurons. In the present study, we investigated the characteristics of Na+ -dependent citrate transport in primary cultures of neurons from mouse cerebral cortex and established the molecular identity of this transport system as the Na+ -coupled citrate transporter (NaC2/NaCT). Reverse transcriptase (RT)-PCR and immunocytochemical analyses revealed that only NaC2/NaCT was expressed in mouse cerebrocortical neurons but not in astrocytes. Uptake of citrate in neurons was Na+ -dependent, Li+ -sensitive, and saturable with the Kt value of 12.3 microM. This Kt value was comparable with that in the case of Na+ -dependent succinate transport (Kt = 9.2 microM). Na+ -activation kinetics revealed that the Na+ -to-citrate stoichiometry was 3.4:1 and concentration of Na+ necessary for half-maximal activation (K0.5(Na)) was 45.7 mM. Na+ -dependent uptake of [14C]citrate (18 microM) was significantly inhibited by unlabeled citrate as well as dicarboxylates such as succinate, malate, fumarate, and alpha-ketoglutarate. This is the first report demonstrating the molecular identity of the Na+ -coupled di/tricarboxylate transport system expressed in neurons as NaC2/NaCT, which can transport the tricarboxylate citrate as well as dicarboxylates such as succinate, alpha-ketoglutarate, and malate.
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PMID:Functional characterization of Na+ -coupled citrate transporter NaC2/NaCT expressed in primary cultures of neurons from mouse cerebral cortex. 1651 67