The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Richard N. Trethewey - One of the best experts on this subject based on the ideXlab platform.
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Potato Hexokinase 2 complements transgenic Arabidopsis plants deficient in Hexokinase 1 but does not play a key role in tuber carbohydrate metabolism
Plant Molecular Biology, 2002Co-Authors: Jon Veramendi, Alisdair R. Fernie, Andrea Leisse, Lothar Willmitzer, Richard N. TretheweyAbstract:Potato plants ( Solanum tuberosum L. cv. Désirée) transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 2 exhibited altered enzyme activities and expression of Hexokinase 2 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed an 11-fold variation in leaf (from 48% of the wild-type activity in antisense transformants to 446% activity in sense transformants) and an 8-fold variation in developing tubers (from 35% of the wild-type activity in antisense transformants to 212% activity in sense transformants). Despite the wide range of Hexokinase activities, no substantial change was found in the fresh weight yield, starch, sugar and metabolite levels of transgenic tubers. However, both potato Hexokinases 1 and 2 were able to complement the hyposensitivity of antisense Hexokinase 1 Arabidopsis transgenic plants to glucose. In an in vitro bioassay of seed germination in a medium with high glucose levels, double transformants showed the same sensitivity to glucose as that of the wild-type ecotype, displaying a stunted phenotype in hypocotyls, cotyledons and roots.
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Potato Hexokinase 2 complements transgenic Arabidopsis plants deficient in Hexokinase 1 but does not play a key role in tuber carbohydrate metabolism
Plant molecular biology, 2002Co-Authors: Jon Veramendi, Alisdair R. Fernie, Andrea Leisse, Lothar Willmitzer, Richard N. TretheweyAbstract:Potato plants (Solanum tuberosum L. cv. Desiree) transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 2 exhibited altered enzyme activities and expression of Hexokinase 2 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed an 11-fold variation in leaf (from 48% of the wild-type activity in antisense transformants to 446% activity in sense transformants) and an 8-fold variation in developing tubers (from 35% of the wild-type activity in antisense transformants to 212% activity in sense transformants). Despite the wide range of Hexokinase activities, no substantial change was found in the fresh weight yield, starch, sugar and metabolite levels of transgenic tubers. However, both potato Hexokinases 1 and 2 were able to complement the hyposensitivity of antisense Hexokinase 1 Arabidopsis transgenic plants to glucose. In an in vitro bioassay of seed germination in a medium with high glucose levels, double transformants showed the same sensitivity to glucose as that of the wild-type ecotype, displaying a stunted phenotype in hypocotyls, cotyledons and roots.
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antisense repression of Hexokinase 1 leads to an overaccumulation of starch in leaves of transgenic potato plants but not to significant changes in tuber carbohydrate metabolism
Plant Physiology, 1999Co-Authors: Jon Veramendi, Lothar Willmitzer, Ute Roessner, Andreas Renz, Richard N. TretheweyAbstract:Potato (Solanum tuberosum L.) plants transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 1 (StHK1) exhibited altered enzyme activities and expression of StHK1 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed a 22-fold variation in leaves (from 22% of the wild-type activity in antisense transformants to 485% activity in sense transformants) and a 7-fold variation in developing tubers (from 32% of the wild-type activity in antisense transformants to 222% activity in sense transformants). Despite the wide range of Hexokinase activities, no change was found in the fresh weight yield, starch, sugar, or metabolite levels of transgenic tubers. However, there was a 3-fold increase in the starch content of leaves from the antisense transformants after the dark period. Starch accumulation at the end of the night period was correlated with a 2-fold increase of glucose and a decrease of sucrose content. These results provide strong support for the hypothesis that glucose is a primary product of transitory starch degradation and is the sugar that is exported to the cytosol at night to support sucrose biosynthesis.
Carlos Gancedo - One of the best experts on this subject based on the ideXlab platform.
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a mutation ser213 asn in the Hexokinase 1 from schizosaccharomyces pombe increases its affinity for glucose
Biochemical and Biophysical Research Communications, 1998Co-Authors: Pilar Herrero, Thomas Petit, Carlos GancedoAbstract:Abstract Alignment of amino acids of the region implicated in glucose binding from a series of Hexokinases showed that Schizosaccharomyces pombe Hexokinase 1 had a Ser residue in a place where all other kinases had an Asn. We changed an AGT codon to AAT to place an Asn in the Ser 213 position. This mutation decreased K m for glucose from 9.4 mM to 1.6 mM and the ratio V max (Fructose)/V max (Glucose) from 5 to 2.5. Also the K m for 2-deoxyglucose decreased from 2.7 mM to 0.8 mM. A mutation in the similar position of S. pombe Hexokinase 2 (Asn 196 /Ser) increased the K m for glucose from 0.16 mM to 0.56 mM. Fermentation of glucose is not detectable in a S. pombe mutant with only Hexokinase 1 activity but expression of the hxk1 S213/N gene conferred ability to ferment the sugar. While the mutated Hexokinase 1 partially mimicked S. cerevisiae Hexokinase II in catabolite repression of invertase, the wild type one could not substitute for it.
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A mutation Ser213/Asn in the Hexokinase 1 from Schizosaccharomyces pombe increases its affinity for glucose.
Biochemical and biophysical research communications, 1998Co-Authors: Thomas Petit, Pilar Herrero, Carlos GancedoAbstract:Abstract Alignment of amino acids of the region implicated in glucose binding from a series of Hexokinases showed that Schizosaccharomyces pombe Hexokinase 1 had a Ser residue in a place where all other kinases had an Asn. We changed an AGT codon to AAT to place an Asn in the Ser 213 position. This mutation decreased K m for glucose from 9.4 mM to 1.6 mM and the ratio V max (Fructose)/V max (Glucose) from 5 to 2.5. Also the K m for 2-deoxyglucose decreased from 2.7 mM to 0.8 mM. A mutation in the similar position of S. pombe Hexokinase 2 (Asn 196 /Ser) increased the K m for glucose from 0.16 mM to 0.56 mM. Fermentation of glucose is not detectable in a S. pombe mutant with only Hexokinase 1 activity but expression of the hxk1 S213/N gene conferred ability to ferment the sugar. While the mutated Hexokinase 1 partially mimicked S. cerevisiae Hexokinase II in catabolite repression of invertase, the wild type one could not substitute for it.
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SCHIZOSACCHAROMYCES POMBE POSSESSES AN UNUSUAL AND A CONVENTIONAL Hexokinase : BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF BOTH HexokinaseS
FEBS Letters, 1996Co-Authors: Thomas Petit, Miguel A Blazquez, Carlos GancedoAbstract:Two Hexokinases were characterized in Schizosaccharomyces pombe: Hexokinase 1, with a low phosphorylation coefficient on glucose (Km 8.5 mM) and Hexokinase 2, a kinetically conventional Hexokinase. Genes hxk1+ and hxk2+ encoding these enzymes were cloned and sequenced. Disruption of hxk1+ had no effect on growth but disruption of hxk2+ doubled the generation time in glucose. Spores carrying the double disruption hxk1+ hxk2+ did not grow on glucose or fructose after one week. Expression of hxk1+ increased strongly during growth in fructose or glycerol. Expression of hxk2+ was highest during growth in glycerol. A NADP-dependent glucose dehydrogenase was detected, but not a glucokinase.
Jon Veramendi - One of the best experts on this subject based on the ideXlab platform.
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Potato Hexokinase 2 complements transgenic Arabidopsis plants deficient in Hexokinase 1 but does not play a key role in tuber carbohydrate metabolism
Plant Molecular Biology, 2002Co-Authors: Jon Veramendi, Alisdair R. Fernie, Andrea Leisse, Lothar Willmitzer, Richard N. TretheweyAbstract:Potato plants ( Solanum tuberosum L. cv. Désirée) transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 2 exhibited altered enzyme activities and expression of Hexokinase 2 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed an 11-fold variation in leaf (from 48% of the wild-type activity in antisense transformants to 446% activity in sense transformants) and an 8-fold variation in developing tubers (from 35% of the wild-type activity in antisense transformants to 212% activity in sense transformants). Despite the wide range of Hexokinase activities, no substantial change was found in the fresh weight yield, starch, sugar and metabolite levels of transgenic tubers. However, both potato Hexokinases 1 and 2 were able to complement the hyposensitivity of antisense Hexokinase 1 Arabidopsis transgenic plants to glucose. In an in vitro bioassay of seed germination in a medium with high glucose levels, double transformants showed the same sensitivity to glucose as that of the wild-type ecotype, displaying a stunted phenotype in hypocotyls, cotyledons and roots.
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Potato Hexokinase 2 complements transgenic Arabidopsis plants deficient in Hexokinase 1 but does not play a key role in tuber carbohydrate metabolism
Plant molecular biology, 2002Co-Authors: Jon Veramendi, Alisdair R. Fernie, Andrea Leisse, Lothar Willmitzer, Richard N. TretheweyAbstract:Potato plants (Solanum tuberosum L. cv. Desiree) transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 2 exhibited altered enzyme activities and expression of Hexokinase 2 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed an 11-fold variation in leaf (from 48% of the wild-type activity in antisense transformants to 446% activity in sense transformants) and an 8-fold variation in developing tubers (from 35% of the wild-type activity in antisense transformants to 212% activity in sense transformants). Despite the wide range of Hexokinase activities, no substantial change was found in the fresh weight yield, starch, sugar and metabolite levels of transgenic tubers. However, both potato Hexokinases 1 and 2 were able to complement the hyposensitivity of antisense Hexokinase 1 Arabidopsis transgenic plants to glucose. In an in vitro bioassay of seed germination in a medium with high glucose levels, double transformants showed the same sensitivity to glucose as that of the wild-type ecotype, displaying a stunted phenotype in hypocotyls, cotyledons and roots.
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antisense repression of Hexokinase 1 leads to an overaccumulation of starch in leaves of transgenic potato plants but not to significant changes in tuber carbohydrate metabolism
Plant Physiology, 1999Co-Authors: Jon Veramendi, Lothar Willmitzer, Ute Roessner, Andreas Renz, Richard N. TretheweyAbstract:Potato (Solanum tuberosum L.) plants transformed with sense and antisense constructs of a cDNA encoding the potato Hexokinase 1 (StHK1) exhibited altered enzyme activities and expression of StHK1 mRNA. Measurements of the maximum catalytic activity of Hexokinase revealed a 22-fold variation in leaves (from 22% of the wild-type activity in antisense transformants to 485% activity in sense transformants) and a 7-fold variation in developing tubers (from 32% of the wild-type activity in antisense transformants to 222% activity in sense transformants). Despite the wide range of Hexokinase activities, no change was found in the fresh weight yield, starch, sugar, or metabolite levels of transgenic tubers. However, there was a 3-fold increase in the starch content of leaves from the antisense transformants after the dark period. Starch accumulation at the end of the night period was correlated with a 2-fold increase of glucose and a decrease of sucrose content. These results provide strong support for the hypothesis that glucose is a primary product of transitory starch degradation and is the sugar that is exported to the cytosol at night to support sucrose biosynthesis.
Radka Kaneva - One of the best experts on this subject based on the ideXlab platform.
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a mutation in an alternative untranslated exon of Hexokinase 1 associated with hereditary motor and sensory neuropathy russe hmsnr
European Journal of Human Genetics, 2009Co-Authors: Janina Hantke, David Chandler, R H M King, Ronald J A Wanders, Dora Angelicheva, Ivailo Tournev, Elyshia Mcnamara, Velina Guergueltcheva, Radka Kaneva, Frank BaasAbstract:Hereditary Motor and Sensory Neuropathy – Russe (HMSNR) is a severe autosomal recessive disorder, identified in the Gypsy population. Our previous studies mapped the gene to 10q22-q23 and refined the gene region to ∼70 kb. Here we report the comprehensive sequencing analysis and fine mapping of this region, reducing it to ∼26 kb of fully characterised sequence spanning the upstream exons of Hexokinase 1 (HK1). We identified two sequence variants in complete linkage disequilibrium, a G>C in a novel alternative untranslated exon (AltT2) and a G>A in the adjacent intron, segregating with the disease in affected families and present in the heterozygote state in only 5/790 population controls. Sequence conservation of the AltT2 exon in 16 species with invariable preservation of the G allele at the mutated site, strongly favour the exonic change as the pathogenic mutation. Analysis of the Hk1 upstream region in mouse mRNA from testis and neural tissues showed an abundance of AltT2-containing transcripts generated by extensive, developmentally regulated alternative splicing. Expression is very low compared with ubiquitous Hk1 and all transcripts skip exon1, which encodes the protein domain responsible for binding to the outer mitochondrial membrane, and regulation of energy production and apoptosis. Hexokinase activity measurement and immunohistochemistry of the peripheral nerve showed no difference between patients and controls. The mutational mechanism and functional effects remain unknown and could involve disrupted translational regulation leading to increased anti-apoptotic activity (suggested by the profuse regenerative activity in affected nerves), or impairment of an unknown HK1 function in the peripheral nervous system (PNS).
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A mutation in an alternative untranslated exon of Hexokinase 1 associated with Hereditary Motor and Sensory Neuropathy – Russe (HMSNR)
European journal of human genetics : EJHG, 2009Co-Authors: Janina Hantke, David Chandler, R H M King, Ronald J A Wanders, Dora Angelicheva, Ivailo Tournev, Elyshia Mcnamara, Velina Guergueltcheva, Marcel S G Kwa, Radka KanevaAbstract:Hereditary Motor and Sensory Neuropathy – Russe (HMSNR) is a severe autosomal recessive disorder, identified in the Gypsy population. Our previous studies mapped the gene to 10q22-q23 and refined the gene region to ∼70 kb. Here we report the comprehensive sequencing analysis and fine mapping of this region, reducing it to ∼26 kb of fully characterised sequence spanning the upstream exons of Hexokinase 1 (HK1). We identified two sequence variants in complete linkage disequilibrium, a G>C in a novel alternative untranslated exon (AltT2) and a G>A in the adjacent intron, segregating with the disease in affected families and present in the heterozygote state in only 5/790 population controls. Sequence conservation of the AltT2 exon in 16 species with invariable preservation of the G allele at the mutated site, strongly favour the exonic change as the pathogenic mutation. Analysis of the Hk1 upstream region in mouse mRNA from testis and neural tissues showed an abundance of AltT2-containing transcripts generated by extensive, developmentally regulated alternative splicing. Expression is very low compared with ubiquitous Hk1 and all transcripts skip exon1, which encodes the protein domain responsible for binding to the outer mitochondrial membrane, and regulation of energy production and apoptosis. Hexokinase activity measurement and immunohistochemistry of the peripheral nerve showed no difference between patients and controls. The mutational mechanism and functional effects remain unknown and could involve disrupted translational regulation leading to increased anti-apoptotic activity (suggested by the profuse regenerative activity in affected nerves), or impairment of an unknown HK1 function in the peripheral nervous system (PNS).
Thomas Petit - One of the best experts on this subject based on the ideXlab platform.
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a mutation ser213 asn in the Hexokinase 1 from schizosaccharomyces pombe increases its affinity for glucose
Biochemical and Biophysical Research Communications, 1998Co-Authors: Pilar Herrero, Thomas Petit, Carlos GancedoAbstract:Abstract Alignment of amino acids of the region implicated in glucose binding from a series of Hexokinases showed that Schizosaccharomyces pombe Hexokinase 1 had a Ser residue in a place where all other kinases had an Asn. We changed an AGT codon to AAT to place an Asn in the Ser 213 position. This mutation decreased K m for glucose from 9.4 mM to 1.6 mM and the ratio V max (Fructose)/V max (Glucose) from 5 to 2.5. Also the K m for 2-deoxyglucose decreased from 2.7 mM to 0.8 mM. A mutation in the similar position of S. pombe Hexokinase 2 (Asn 196 /Ser) increased the K m for glucose from 0.16 mM to 0.56 mM. Fermentation of glucose is not detectable in a S. pombe mutant with only Hexokinase 1 activity but expression of the hxk1 S213/N gene conferred ability to ferment the sugar. While the mutated Hexokinase 1 partially mimicked S. cerevisiae Hexokinase II in catabolite repression of invertase, the wild type one could not substitute for it.
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A mutation Ser213/Asn in the Hexokinase 1 from Schizosaccharomyces pombe increases its affinity for glucose.
Biochemical and biophysical research communications, 1998Co-Authors: Thomas Petit, Pilar Herrero, Carlos GancedoAbstract:Abstract Alignment of amino acids of the region implicated in glucose binding from a series of Hexokinases showed that Schizosaccharomyces pombe Hexokinase 1 had a Ser residue in a place where all other kinases had an Asn. We changed an AGT codon to AAT to place an Asn in the Ser 213 position. This mutation decreased K m for glucose from 9.4 mM to 1.6 mM and the ratio V max (Fructose)/V max (Glucose) from 5 to 2.5. Also the K m for 2-deoxyglucose decreased from 2.7 mM to 0.8 mM. A mutation in the similar position of S. pombe Hexokinase 2 (Asn 196 /Ser) increased the K m for glucose from 0.16 mM to 0.56 mM. Fermentation of glucose is not detectable in a S. pombe mutant with only Hexokinase 1 activity but expression of the hxk1 S213/N gene conferred ability to ferment the sugar. While the mutated Hexokinase 1 partially mimicked S. cerevisiae Hexokinase II in catabolite repression of invertase, the wild type one could not substitute for it.
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SCHIZOSACCHAROMYCES POMBE POSSESSES AN UNUSUAL AND A CONVENTIONAL Hexokinase : BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF BOTH HexokinaseS
FEBS Letters, 1996Co-Authors: Thomas Petit, Miguel A Blazquez, Carlos GancedoAbstract:Two Hexokinases were characterized in Schizosaccharomyces pombe: Hexokinase 1, with a low phosphorylation coefficient on glucose (Km 8.5 mM) and Hexokinase 2, a kinetically conventional Hexokinase. Genes hxk1+ and hxk2+ encoding these enzymes were cloned and sequenced. Disruption of hxk1+ had no effect on growth but disruption of hxk2+ doubled the generation time in glucose. Spores carrying the double disruption hxk1+ hxk2+ did not grow on glucose or fructose after one week. Expression of hxk1+ increased strongly during growth in fructose or glycerol. Expression of hxk2+ was highest during growth in glycerol. A NADP-dependent glucose dehydrogenase was detected, but not a glucokinase.