Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzymatic method of H. W. Schiwara (1972) Z. Klim. Chem. Klin. Biochem. 10,12--16 (reagents by Smith Kline Instruments), using the enzymatic reaction sequence alpha-amylase -- alpha-glucosidase -- hexokinase/glucose 6-phosphate dehydrogenase for the determination of alpha-amylase was evaluated on the ABA-100. The coefficient of variation for control sera and human pooled serum was 0.9--4.2% within series, and 1.4--6.6% day to day. Reference values for a healthy population (212 blood donors) in sera were 13--79 U/1 (+/- 2 SD), mean 46 U/1. In catch urines the values did not show a normal distribution; the minimal and maximal range for men was 58--385 U/1, for women 7--318 U/1. The kinetic curve of the enzymatic test was measured and the influence of glucose and linearity studied. In comparison with the enzymatic test, the chromogenic method Amlyochrom Roche was tested on the sera and urine of patients. The coefficient of correlation in sera was r = 0.975, in urine r = 0.965.
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PMID:[Determination of alpha-amylase by an enzymatic kinetic method on the ABA-100 (author's transl)]. 37 66

Studies are reported on the reaction kinetics of the glucose assay according to Trinder which involves the specific oxidation of glucose by glucose oxidase and the determination of the hydrogen peroxide released by means of phenol and 4-aminophenazone in the presence of peroxidase. The results have been used to develop a general kinetic fixed-time method for the analysis of glucose in whole blood and serum. The single reagent method has been adapted to the ENI GEMSAEC centrifugal analyzer and to the Abbott ABA-100 analyzer. The procedures exhibited excellent precision and the results correlated well with those obtained by the hexokinase method, Linearity was achieved from 3 to 64 mmol/1 glucose for the GEMSAEC method, and from 3 to 33 mmol/1 glucose for the ABA-100 method. Reagent or sample blank corrections were not necessary. There were no interferences from various drugs, hemoglobin, bilirubin, or lipemia.
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PMID:Kinetic enzymatic method for automated determination of glucose in blood and serum. 83 60

This report summarizes a one year evaluation of Abbott's ABA 100, with respect to mechanical parts (syringe plates, precision and linearity of photometry, band width of several filters, multicuvet precision, temperature control) and the reliability of several methods (endpoint procedures: determination of the glucose concentration with hexokinase- and the glucose dehydrogenase method, and of the protein concentration; enzyme activities: alanine and aspartate aminotransferase, creatine kinase, alkaline phosphatase). The critical batch size was estimated as an indicator of economy (about 40 samples per day for the glucose concentration). Various aspects of the instrument are discussed with respect to its use in clinical chemistry.
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PMID:Evaluation of the Abbott Bichromatic Analyzer 100 (A proposal for an evaluation scheme). 95 29

In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described ABSCISIC ACID INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of abscisic acid and components of the abscisic acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an abscisic acid- and sugar-dependent way.
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PMID:The Arabidopsis SUCROSE UNCOUPLED-6 gene is identical to ABSCISIC ACID INSENSITIVE-4: involvement of abscisic acid in sugar responses. 1097 84

Of the growing list of promising genes for plant improvement, some of the most versatile appear to be those involved in sugar alcohol metabolism. Mannitol, one of the best characterized sugar alcohols, is a significant photosynthetic product in many higher plants. The roles of mannitol as both a metabolite and an osmoprotectant in celery (Apium graveolens) are well documented. However, there is growing evidence that 'metabolites' can also have key roles in other environmental and developmental responses in plants. For instance, in addition to its other properties, mannitol is an antioxidant and may have significant roles in plant-pathogen interactions. The mannitol catabolic enzyme mannitol dehydrogenase (MTD) is a prime modulator of mannitol accumulation in plants. Because the complex regulation of MTD is central to the balanced integration of mannitol metabolism in celery, its study is crucial in clarifying the physiological role(s) of mannitol metabolism in environmental and metabolic responses. In this study we used transformed Arabidopsis to analyze the multiple environmental and metabolic responses of the Mtd promoter. Our data show that all previously described changes in Mtd RNA accumulation in celery cells mirrored changes in Mtd transcription in Arabidopsis. These include up-regulation by salicylic acid, hexokinase-mediated sugar down-regulation, and down-regulation by salt, osmotic stress and ABA. In contrast, the massive up-regulation of Mtd expression in the vascular tissues of salt-stressed Arabidopsis roots suggests a possible role for MTD in mannitol translocation and unloading and its interrelation with sugar metabolism.
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PMID:Analysis of celery (Apium graveolens) mannitol dehydrogenase (Mtd) promoter regulation in Arabidopsis suggests roles for MTD in key environmental and metabolic responses. 1172 47

Elongation of carrot somatic embryo radicles was inhibited by sucrose at or above 5% (145 mM). This effect would not be released until the sucrose concentration was lowered again. Morphological and cytological studies as well as determination of ABA content and analysis of the expression mode of a Lea gene, all point to its similarity to natural dormancy and germination of seeds. Use of monosaccharides (glucose and fructose), other disaccharide (maltose), and isomolar concentration of osmotica (mannitol and sorbitol), did not show similar regulatory effect. It is thus clear that the regulatory effect is not a result of simple osmotic stress. Hexokinase inhibitors such as glucosamine and N -acetyl-glucosamine did not exert any influence on the regulation-deregulation effects of sucrose. Mannose, which inhibits germination of Arabidopsis seeds, did not prevent carrot somatic embryo radicles from elongating. It is thus inferred that this sucrose-signaling pathway may be independent of hexokinase. As a first step to understand the molecular mechanism of this process, a carrot sucrose transporter gene ( cSUT ) expressed in the embryos and roots specifically was isolated. Studies on transformed yeast mutant with cSUT cDNA identified its sucrose transport activity. Northern hybridization and gel retardation experiment revealed that there is a marked increase in expression of cSUT at the beginning of somatic embryo germination, and this is attributed to regulation on the level of transcription. This suggested the possibility that cSUT has an important role in this sucrose signal regulation system.
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PMID:Sucrose regulates elongation of carrot somatic embryo radicles as a signal molecule. 1528 98

ABI4 encodes an AP2 family transcription factor that is a central regulator in sugar responsive gene expression in plants. Sugar-induced ABI4 regulates plant genes essential for photosynthesis, and carbon, nitrogen and lipid metabolism. ABI4 activity is induced via the ABA-mediated sugar signalling pathway, which is initiated by the glucose sensing protein hexokinase. Natural variation in sugar sensitivity was used to identify new loci involved in sugar signalling. Five quantitative trait loci (QTLs) for glucose sensitivity (GSQ1-GSQ5) were identified in a Ler/Cvi recombinant inbred line (RIL) population. The GSQ3, GSQ4 and GSQ5 loci are positioned in regions not previously associated with known sugar-sensing genes. GSQ5 was fine mapped and cloned using a candidate-gene approach. The GSQ5 locus was shown to encode the DELAY OF GERMINATION 1 (DOG1) gene. DOG1 was previously identified as a major locus in seed dormancy control. Glucose addition induced the expression of the GSQ5/DOG1 Cvi allele, whereas the Ler and Col alleles did not respond to glucose. Positive feedback was observed between the ABA-mediated sugar signalling pathway and the GSQ5/DOG1 Cvi allele. Expression of the GSQ5/DOG1 Cvi allele requires the ABA-mediated sugar signalling pathway, of which ABI4 is an important component. In addition, sugar induction of ABI4 was promoted by the GSQ5/DOG1 Cvi allele.
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PMID:The Arabidopsis GSQ5/DOG1 Cvi allele is induced by the ABA-mediated sugar signalling pathway, and enhances sugar sensitivity by stimulating ABI4 expression. 1841 Apr 83

Photosynthesis is regulated by environmental factors as well as endogenous sugar signals. Whereas light-driven sugar biosynthesis is essential for terrestrial organisms, as well as belowground microflora, whether and how soil symbionts regulate photosynthesis has yet to be reported. Here, we show that the plant growth-promoting soil bacterium Bacillus subtilis GB03 augments photosynthetic capacity by increasing photosynthetic efficiency and chlorophyll content in Arabidopsis. Mechanistic studies reveal an elevation of sugar accumulation as well as the suppression of classic glucose signaling responses, including hypocotyl elongation and seed germination, with exposure to GB03. Compared with wild-type plants, two Arabidopsis mutants defective in hexokinase-dependent sugar signaling exhibit increased photosynthetic capacity, which is not further enhanced with GB03 exposure. Overlap in sugar/ABA sensing is observed in GB03-exposed plants, with a reduction of ABA-biosynthetic transcripts as well as downstream metabolite levels in leaves. Moreover, exogenous ABA abrogates GB03-triggered increases in photosynthetic efficiency and chlorophyll content. These results demonstrate that certain rhizobacteria elevate photosynthesis through the modulation of endogenous sugar/ABA signaling, and establish a regulatory role for soil symbionts in plant acquisition of energy.
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PMID:Soil bacteria augment Arabidopsis photosynthesis by decreasing glucose sensing and abscisic acid levels in planta. 1857 92

Starch branching enzyme (SBE) activity in the cassava storage root exhibited a diurnal fluctuation, dictated by a transcriptional oscillation of the corresponding SBE genes. The peak of SBE activity coincided with the onset of sucrose accumulation in the storage, and we conclude that the oscillatory mechanism keeps the starch synthetic apparatus in the storage root sink in tune with the flux of sucrose from the photosynthetic source. When storage roots were uncoupled from the source, SBE expression could be effectively induced by exogenous sucrose. Turanose, a sucrose isomer that cannot be metabolized by plants, mimicked the effect of sucrose, demonstrating that downstream metabolism of sucrose was not necessary for signal transmission. Also glucose and glucose-1-P induced SBE expression. Interestingly, induction by sucrose, turanose and glucose but not glucose-1-P sustained an overt semidian (12-h) oscillation in SBE expression and was sensitive to the hexokinase (HXK) inhibitor glucosamine. These results suggest a pivotal regulatory role for HXK during starch synthesis. Abscisic acid (ABA) was another potent inducer of SBE expression. Induction by ABA was similar to that of glucose-1-P in that it bypassed the semidian oscillator. Both the sugar and ABA signaling cascades were disrupted by okadaic acid, a protein phosphatase inhibitor. Based on these findings, we propose a model for sugar signaling in regulation of starch synthesis in the cassava storage root.
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PMID:Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis. 1951 34

Tandem zinc finger (TZF) proteins are characterized by two zinc-binding CCCH motifs arranged in tandem. Human TZFs such as tristetraproline (TTP) bind to and trigger the degradation of mRNAs encoding cytokines and various regulators. Although the molecular functions of plant TZFs are unknown, recent genetic studies have revealed roles in hormone-mediated growth and environmental responses, as well as in the regulation of gene expression. Here we show that expression of AtTZF1 (AtCTH/AtC3H23) mRNA is repressed by a hexokinase-dependent sugar signaling pathway. However, AtTZF1 acts as a positive regulator of ABA/sugar responses and a negative regulator of GA responses, at least in part by modulating gene expression. RNAi of AtTZF1-3 caused early germination and slightly stress-sensitive phenotypes, whereas plants over-expressing AtTZF1 were compact, late flowering and stress-tolerant. The developmental phenotypes of plants over-expressing AtTZF1 were only partially rescued by exogenous application of GA, implying a reduction in the GA response or defects in other mechanisms. Likewise, the enhanced cold and drought tolerance of plants over-expressing AtTZF1 were not associated with increased ABA accumulation, suggesting that it is mainly ABA responses that are affected. Consistent with this notion, microarray analysis showed that over-expression of AtTZF1 mimics the effects of ABA or GA deficiency on gene expression. Notably, a gene network centered on a GA-inducible and ABA/sugar-repressible putative peptide hormone encoded by GASA6 was severely repressed by AtTZF1 over-expression. Hence AtTZF1 may serve as a regulator connecting sugar, ABA, GA and peptide hormone responses.
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PMID:The Arabidopsis tandem zinc finger protein AtTZF1 affects ABA- and GA-mediated growth, stress and gene expression responses. 2122 90


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