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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glucose-6-phosphate dehydrogenase (EC 1.1.1.49) gene (zwf) of the cyanobacterium Synechococcus PCC 7942 was cloned on a 2.8 kb Hind III fragment. Sequence analysis revealed an ORF of 1572 nucleotides encoding a polypeptide of 524 amino acids which exhibited 41% identity with the glucose-6-phosphate dehydrogenase of Escherichia coli.
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PMID:Cloning and sequence analysis of the glucose-6-phosphate dehydrogenase gene from the cyanobacterium Synechococcus PCC 7942. 164 89

A mutant of the cyanobacterium Synechococcus sp. strain PCC 7942 carrying a disrupted gene encoding glucose-6-phosphate dehydrogenase (zwf) produced no detectable glucose-6-phosphate dehydrogenase as assessed by enzyme assay and Western blot (immunoblot) analysis. This mutant exhibited significantly impaired dark viability.
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PMID:Characterization of a zwf mutant of Synechococcus sp. strain PCC 7942. 773 Feb 89

The region of the genome encoding the glucose-6-phosphate dehydrogenase gene zwf was analysed in a unicellular cyanobacterium, Synechococcus sp. PCC 7942, and a filamentous, heterocystous cyanobacterium, Anabaena sp. PCC 7120. Comparison of cyanobacterial zwf sequences revealed the presence of two absolutely conserved cysteine residues which may be implicated in the light/dark control of enzyme activity. The presence in both strains of a gene fbp, encoding fructose-1,6-bisphosphatase, upstream from zwf strongly suggests that the oxidative pentose phosphate pathway in these organisms may function to completely oxidize glucose 6-phosphate to CO2. The amino acid sequence of fructose-1,6-bisphosphatase does not support the idea of its light activation by a thiol/disulfide exchange mechanism. In the case of Anabaena sp. PCC 7120, the tal gene, encoding transaldolase, lies between zwf and fbp.
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PMID:A comparison of gene organization in the zwf region of the genomes of the cyanobacteria Synechococcus sp. PCC 7942 and Anabaena sp. PCC 7120. 856 7

The syntheses of three classes of C-3 perfluoroalkyl substituted steroids are described. They are the 3 beta-hydroxy-3 alpha-perfluoroalkylandrost-4-en-17-ones (5a-c), 3-perfluoroalkylandrosta-3,5-dien-3-ones (8a-c) and 3 beta-hydroxy-3 alpha-perfluoroalkylandrost-5-en-17-ones (12a-c). Addition of a series of perfluoroalkylorganometallic reagents (RFLi; RF = C2F5, C3F7, or C4F9) to the 3 position of silylated testosterone 2b afforded delta 4 perfluoroalkyl carbinols 3. In Scheme 1, deprotection with HF and oxidation at the C-17 carbon with PCC produced delta 4 ketones 5. In Scheme 2 dehydration of 3 with 1,2-phenylenephosphorochloridite and iodine afforded delta 3,5 dienes 6 which were deprotected and oxidized as above to the C-17 ketones 8. In Scheme 3 isomerization of the double bond of 3 from the C-4 to the C-5 position using the allylic halogenation followed by treatment with lithium aluminum hydride led to the synthesis of the double bond isomer series 12. A new method for dehydration was developed. On average and within experimental error, 3 beta-hydroxy-3 alpha-perfluoroalkylandrost-5-en-17 ones (12a-c) were better than the 3-perfluoroalkylandrosta-3,5-dien-17-ones (8a-c) and 3 beta-hydroxy-3 alpha-perfluoroalkylandrost-4-en-17-ones (5a-c) at inhibiting glucose-6-phosphate dehydrogenase.
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PMID:The syntheses of 3-substituted perfluoroalkyl steroids. 875 Apr 32

Glucose-6-phosphate dehydrogenase is a particularly important enzyme in carbon catabolism in the chloroplasts of higher plants and in cyanobacteria. It catalyzes the first reaction in the oxidative pentose phosphate pathway which supplies reduced NADP for a variety of biosynthetic processes. The enzyme is known to be regulated by light. However, the dehydrogenase from plants has been difficult to purify and there is little information on kinetics and mechanism of deactivation. The glucose-6-phosphate dehydrogenase from the heterocystous cyanobacterium, Anabaena sp. PCC 7120, was purified to near homogeneity by chromatography on 2',5'-ADP Sepharose chromatography. The cyanobacterial enzyme apparently has different aggregation states or conformations depending on its concentration in solution and the pH. At a pH of 8.0 and low ionic strength, the enzyme has relatively low activity and exhibits sigmoidal kinetics on binding substrate and cofactor. Activity increases and the enzyme exhibits the more classical hyperbolic kinetics at pH 7.0. At the lower pH, glucose-6-phosphate dehydrogenase is inhibited by catalytic amounts of reduced thioredoxin-1 from Anabaena sp. The second thioredoxin from the cyanobacterium is much less effective, although its inhibitory effect is still greater than that of small molecule reducing agents such as glutathione. Glutamine was reported to stabilize the isolated enzyme, but actually is an activator at pH 8.0. The results suggest that cellular demand for reduced cofactor under nitrogen-fixing conditions overrides the pH-induced deactivation.
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PMID:Glucose-6-phosphate dehydrogenase from the cyanobacterium, Anabaena sp. PCC 7120: purification and kinetics of redox modulation. 890 Apr 2

Multiple molecular forms of glucose-6-phosphate dehydrogenase (G6PDH) were detected by activity staining in non-denaturing polyacrylamide gels of cell-free extracts from a range of cyanobacteria including Anabaena sp. PCC 7120, Synechococcus sp. PCC 7942, Plectonema boryanum PCC 73110, Synechocystis sp. PCC 6803, Nostoc sp. MAC PCC 8009 and the marine strain Synechococcus sp. WH7803. In most of the species tested, the profile of G6PDH activities was modulated by the growth of the cells in the presence of exogenous 10 mM glucose. Using an antiserum raised against a fragment of G6PDH from Anabaena sp. PCC 7120, it was shown that the different molecular forms of G6PDH all contained an antigenically related subunit, suggesting that the different forms arose from different quaternary structures involving the same monomer. An insertion mutant of Synechococcus sp. PCC 7942 was constructed in which the opcA gene, adjacent to zwf (encoding G6PDH), was disrupted. Although no reduction in the amount of G6PDH monomers (Zwf) was observed in the opcA mutant, activity staining of native gels indicated that most of this protein is not assembled into one of the active oligomeric forms. The oligomerization of G6PDH in extracts of the opcA mutant was stimulated in vitro by a factor present in crude extracts of the wild-type, suggesting that the product of the opcA gene is involved in the oligomerization and activation of G6PDH.
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PMID:Multiple oligomeric forms of glucose-6-phosphate dehydrogenase in cyanobacteria and the role of OpcA in the assembly process. 963 25

Gene expression in the cyanobacterium Synechococcus elongatus PCC 7942 is under the control of a circadian oscillator, such that peaks and troughs of expression recur with a periodicity of about 24 h in the absence of environmental cues. This can be monitored easily as light production from luciferase gene fusions to S. elongatus promoters. All promoters seem to exhibit circadian oscillation of expression, but the phasing of peak and trough times differs among different genes. The majority of genes are designated class 1, with expression peaks near dusk or subjective dusk (the time corresponding to dusk in the absence of a diurnal cycle). A minority, of which purF is an example, have expression peaks approximately 12 h out of phase with class 1 genes. A screen of Tn5 mutants for those in which purF phasing is altered revealed a mutant that carries an insertion in the opcA gene, previously identified as essential for glucose-6-phosphate dehydrogenase function. However, a different enzymatic reporter and in vitro luciferase assays revealed that the expression pattern of the purF promoter is not altered by opcA inactivation, but rather the reduced flavin mononucleotide substrate of luciferase is limiting at the time of the natural circadian peak. The results suggest that OpcA is involved in temporally separated reductant-generating pathways in S. elongatus and that it has a role outside of its function in activating glucose-6-phosphate dehydrogenase. The opcA gene, expected to be cotranscribed with fbp and zwf, was shown to have its own class 2 promoter, whereas the fbp promoter was determined to be in class 1. Thus, opcA expression is likely to be constitutive by virtue of the activity of two promoters in nearly opposite circadian phases.
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PMID:A new circadian class 2 gene, opcA, whose product is important for reductant production at night in Synechococcus elongatus PCC 7942. 1102 44

Activities of glucokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase, phosphofructokinase (PFK), enolase, pyruvate kinase (PK) and phosphoenolpyruvate (PEP) carboxylase were determined in extracts of photoautotrophic, mixotrophic, and heterotrophic cultures of Synechocystis sp. PCC 6803. Annotated genomes of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 were analyzed for the respective predicted physical properties of each enzyme investigated here. Enzymatic activity was largely unaffected by nutritional mode, with the exception of glucokinase and PK whose activities were significantly elevated in heterotrophic cultures of Synechocystis sp. PCC 6803. PFK activity was insensitive to bacterial PFK-A (allosteric) effectors such as PEP, implying that Synechocystis PFK should be classified as a PFK-B (non-allosteric). Immunoblot and kinetic studies indicated that irrespective of nutritional mode, the Synechocystis PK corresponds to a PK-A (AMP activated) rather than PK-F (fructose-1,6-bisphosphate activated).
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PMID:From genome to enzyme: analysis of key glycolytic and oxidative pentose-phosphate pathway enzymes in the cyanobacterium Synechocystis sp. PCC 6803. 1288 4

The deletion of a gene coding for a histidine kinase (sll0750, Hik8) in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 resulted in a conditional lethal phenotype with a pleiotropic effect on the expression of genes involved in glucose metabolism. This mutant had comparable doubling times to wild type (WT) in continuous-light-grown photoautotrophic and mixotrophic cultures, whereas it grew poorly under mixotrophic conditions with different light and dark cycles. Growth was completely stopped, and cells eventually died, when the light duration was less than 6 h on a 24-h regimen. Northern blot analysis demonstrated that steady-state transcript levels of genes encoding key enzymes of glycolysis, gluconeogenesis, the oxidative pentose phosphate pathway, and glycogen metabolism were significantly altered in a strain with mutant hik8 (Deltahik8) grown with or without glucose. In some cases, differential expression was dependent on growth conditions (photoautotrophic versus mixotrophic). The enzyme activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and phosphofructokinase were significantly reduced in Deltahik8 compared to WT. Glycogen determination indicated that Deltahik8 accumulated glycogen under mixotrophic conditions but was unable to utilize these reserves for heterotrophic growth. The results suggest that the loss of gap1 transcription in the absence of Hik8 was the key factor that rendered cells unable to catabolize glucose and grow heterotrophically. Additionally, the transcript levels of the phytochrome gene (cph1) and its cotranscribed response regulator gene (rcp1) were significantly reduced and its dark inducibility was lost in Deltahik8. The results demonstrated that Hik8 plays an important role in glucose metabolism and is necessary for heterotrophic growth.
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PMID:Pleiotropic effect of a histidine kinase on carbohydrate metabolism in Synechocystis sp. strain PCC 6803 and its requirement for heterotrophic growth. 1577 80

The sigE gene of Synechocystis sp. PCC 6803 encodes a group 2 sigma factor for RNA polymerase and has been proposed to function in transcriptional regulation of nitrogen metabolism. By using microarray and Northern analyses, we demonstrated that the abundance of transcripts derived from genes important for glycolysis, the oxidative pentose phosphate pathway, and glycogen catabolism is reduced in a sigE mutant of Synechocystis maintained under the normal growth condition. Furthermore, the activities of the two key enzymes of the oxidative pentose phosphate pathway, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, encoded by the zwf and gnd genes were also reduced in the sigE mutant. The dark enhancements in both enzyme activity and transcript abundance apparent in the wild type were eliminated by the mutation. In addition, the sigE mutant showed a reduced rate of glucose uptake and an increased intracellular level of glycogen. Moreover, it was unable to proliferate under the light-activated heterotrophic growth conditions. These results indicate that SigE functions in the transcriptional activation of sugar catabolic pathways in Synechocystis sp. PCC 6803.
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PMID:Positive regulation of sugar catabolic pathways in the cyanobacterium Synechocystis sp. PCC 6803 by the group 2 sigma factor sigE. 1594 48


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