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101.
Fructose 2,6-bisphosphate affects phosphoglucomutase from plant and animal sources in a similar way. As previously found with rabbit muscle phosphoglucomutase, fructose 2,6-bisphosphate cannot substitute for glucose 1,6-bisphosphate as a cofactor in the reaction catalyzed by phosphoglucomutase from potato tubers, pea seeds, and string-beans. In the presence of glucose 1,6-bisphosphate, fructose 2,6-bisphosphate inhibits phosphoglucomutase from potato tubers. Activation of phosphoglucomutase from plant sources by fructose 2,6-bisphosphate reported by others was probably due to contamination of the commercial preparation of fructose 2,6-bisphosphate by glucose 1,6-bisphosphate. 相似文献
102.
Fructose 2, 6-Bisphosphate in Hypoglycemic Rat Brain 总被引:2,自引:2,他引:0
Santiago Ambrosio Francesc Ventura Jose Luis Rosa Ramon Bartrons 《Journal of neurochemistry》1991,57(1):200-203
Abstract: Fructose 2,6-bisphosphate has been studied during hypoglycemia induced by insulin administration (40 IU/kg). No changes in content of cerebral fructose 2,6-bisphosphate were found in mild hypoglycemia, but the level of this compound was markedly decreased in hypoglycemic coma and recovered after 30 min of glucose administration. To correlate a possible modification of the concentration of the metabolite with selective regional damage occurring during hypoglycemic coma, we have analyzed four cerebral areas (cortex, striatum, cerebellum, and hippocampus). Fructose 2,6-bisphosphate concentrations were similar in the four areas analyzed; severe hypoglycemia decreased levels of the metabolite to the same extent in all the brain areas studied. The decrease in content of fructose 2,6-bisphosphate was not always accompanied by a parallel decrease in ATP levels, a result suggesting that the low levels of the bisphosphorylated metabolite during hypoglycemic coma could be due to the decreased 6-phosphofructo-2-kinase activity, mainly as a consequence of the fall in concentration of its substrate (fructose 6-phosphate). These results suggest that fructose 2,6-bisphosphate could play a permissive role in cerebral tissue, maintaining activation of 6-phosphofructo-l-kinase and glycolysis. 相似文献
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Fructose 2,6-bisphosphate and 6-phosphofructo-2-kinase during liver regeneration. 总被引:2,自引:0,他引:2 下载免费PDF全文
Glycogen and fructose 2,6-bisphosphate levels in rat liver decreased quickly after partial hepatectomy. After 7 days the glycogen level was normalized and fructose 2,6-bisphosphate concentration still remained low. The 'active' (non-phosphorylated) form of 6-phosphofructo-2-kinase varied in parallel with fructose 2,6-bisphosphate levels, whereas the 'total' activity of the enzyme decreased only after 24 h, similarly to glucokinase. The response of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from hepatectomized rats (96 h) to sn-glycerol 3-phosphate and to cyclic AMP-dependent protein kinase was different from that of the enzyme from control animals and similar to that of the foetal isoenzyme. 相似文献
107.
Busquets S Garcia-Martínez C Olivan M Barreiro E López-Soriano FJ Argilés JM 《Biochimica et biophysica acta》2006,1760(2):253-258
Overexpression of the UCP3 gene in both murine and human myotube cell cultures leads to a significant activation of the different proteolytic systems involved in muscle myofibrillar protein breakdown. Thus, lysosomal (cathepsin B) and non-lysosomal (m-calpain and ubiquitin-proteasome) mRNA content was significantly increased in the different cell culture systems used. Interestingly, the overexpression of the UCP3 gene was not associated with any changes in apoptosis. Although the function of the UCP3 protein is not completely understood (uncoupling, oxidative stress), these results suggest a possible relation between these main mechanisms involved in muscle wasting during cancer. 相似文献
108.
Plasmid replication initiator RepB forms a hexamer reminiscent of ring helicases and has mobile nuclease domains 下载免费PDF全文
D Roeland Boer José A Ruíz‐Masó José R López‐Blanco Alexander G Blanco Mireia Vives‐Llàcer Pablo Chacón Isabel Usón F Xavier Gomis‐Rüth Manuel Espinosa Oscar Llorca Gloria del Solar Miquel Coll 《The EMBO journal》2009,28(11):1666-1678
RepB initiates plasmid rolling‐circle replication by binding to a triple 11‐bp direct repeat (bind locus) and cleaving the DNA at a specific distant site located in a hairpin loop within the nic locus of the origin. The structure of native full‐length RepB reveals a hexameric ring molecule, where each protomer has two domains. The origin‐binding and catalytic domains show a three‐layer α–β–α sandwich fold. The active site is positioned at one of the faces of the β‐sheet and coordinates a Mn2+ ion at short distance from the essential nucleophilic Y99. The oligomerization domains (ODs), each consisting of four α‐helices, together define a compact ring with a central channel, a feature found in ring helicases. The toroidal arrangement of RepB suggests that, similar to ring helicases, it encircles one of the DNA strands during replication to confer processivity to the replisome complex. The catalytic domains appear to be highly mobile with respect to ODs. This mobility may account for the adaptation of the protein to two distinct DNA recognition sites. 相似文献
109.
Mireia Junyent Katherine L. Tucker Caren E. Smith Antonio Garcia-Rios Josiemer Mattei Chao-Qiang Lai Laurence D. Parnell Jose M. Ordovas 《Journal of lipid research》2009,50(3):565-573
Low HDL-cholesterol (HDL-C) is associated with an increased risk for atherosclerosis, and concentrations are modulated by genetic factors and environmental factors such as smoking. Our objective was to assess whether the association of common single-nucleotide polymorphisms (SNPs) at ABCG5/G8 (i18429G>A, i7892T>C, Gln604GluC>G, 5U145A>C, Tyr54CysA>G, Asp19HisG>C, i14222A>G, and Thr400LysC>A) genes with HDL-C differs according to smoking habit. ABCG5/G8 SNPs were genotyped in 845 participants (243 men and 602 women). ABCG5/G8 (i7892T>C, 5U145A>C, Tyr54CysA>G, Thr400LysC>A) SNPs were significantly associated with HDL-C concentrations (P < 0.001–0.013) by which carriers of the minor alleles at the aforementioned polymorphisms and homozygotes for the Thr400 allele displayed lower HDL-C. A significant gene-smoking interaction was found, in which carriers of the minor alleles at ABCG5/G8 (Gln604GluC>G, Asp19HisG>C, i14222A>G) SNPs displayed lower concentrations of HDL-C only if they were smokers (P = 0.001–0.025). Also, for ABCG8_Thr400LysC>A SNP, smokers, but not nonsmokers, homozygous for the Thr400 allele displayed lower HDL-C (P = 0.004). Further analyses supported a significant haplotype global effect on lowering HDL-C (P = 0.002) among smokers. In conclusion, ABCG5/G8 genetic variants modulate HDL-C concentrations, leading to an HDL-C-lowering effect and thereby a potential increased risk for atherosclerosis only in smokers. 相似文献
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