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Purification and characterization of Ascaris suum hexokinase

Description: A procedure for purifying hexokinase from Ascaris muscle has been developed. The physical and catalytic properties of the enzyme are comparable to mammalian hexokinases. The enzyme is a monomer with a molecular weight of 100,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration.
Date: August 1975
Creator: Supowit, Scott C.
Partner: UNT Libraries

Molecular mechanisms of enhanced [18F] fluorodeoxy glucose (FDG) uptake in isochemically injured myocardium: the role of glucose transporter and hexokinase expression. Final technical report for period August 1, 1993--November 30, 1997

Description: We determined that there were no regional differences in GLUT1 or GLUT4 expression in normal dog heart. We demonstrated that glucose uptake was relatively enhanced in regions of severe ischemia in this model. We showed that GLUT1 mRNA and polypeptide expression but not GLUT4 expression were substantially and significantly increased in both ischemic and nonischemic myocardial regions after 6 hours. We also found that GLUT4 translocation and glucose uptake induced by ischemia in perfused rat hearts were not inhibited by Wortmannin, a PI3 kinase inhibitor, whereas insulin-stimulatd increases in GLUT4 translocation and glucose uptake were inhibited. To determine whether some of the same phenomena occurred in humans with chronic myocardial ischemia, we investigated myocardial GLUT mRNA expression in 11 patients who underwent coronary artery bypass surgery. We have cultured neonatal rat cardiomyocytes and tested the effects of several factors including hypoxia and insulin.
Date: August 1, 1999
Creator: Brosius, F.C. III
Partner: UNT Libraries Government Documents Department

Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis

Description: 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.
Date: January 15, 2008
Creator: Jansson, Christer; Baguma, Yona; Sun, Chuanxin; Boren, Mats; Olsson, Helena; Rosenqvist, Sara et al.
Partner: UNT Libraries Government Documents Department

Sucrose-mediated transcriptional regulation of sucrose symporter activity in the phloem.

Description: This project was based on our discovery that sucrose acts as a signaling molecule that regulates the activity of a proton-sucrose symporter in sugar beet leaf tissue. A major objective here was determining how sucrose transporter activity is being regulated. When sucrose accumulates in the phloem sucrose transport activity drops dramatically. Western blots of plasma membrane proteins isolated from sucrose treated leaves showed that the loss of sucrose transport activity was proportional to a decline in symporter abundance, demonstrating that sucrose transport is regulated by changes in the amount of BvSUT1 protein. BvSUT1 transcript levels decreased in parallel with the loss of sucrose transport activity. Nuclear run-on experiments demonstrated that BvSUT1 gene transcription was repressed significantly in nuclei from leaves fed 100 mM exogenous sucrose, showing that sucrose-dependent modulation of BvSUT1 mRNA levels is mediated by changes in transcription. To identify which secondary messenger systems might be involved in regulating symporter activity, we used a variety of pharmacological agents to probe for a role of calcium or protein phosphorylation in sucrose signaling. In a detailed analysis, only okadaic acid altered sucrose transport activity. These results suggest a protein phosphatase is involved. We hypothesized that protein kinase inhibitors would have a neutral affect or increase symporter transcription. Transpirational feeding of the protein kinase inhibitor staurosporine had no impact on sucrose transport while calphostin C, an inhibitor of protein kinase C, caused a 60% increase. These data provided good evidence that protein phosphorylation plays a central role in regulating sucrose symporter expression and sucrose transport activity. To determine whether protein phosphorylation is involved in sucrose regulation of proton-sucrose symporter activity, we pre-fed leaves with staurosporine for 4 h and then fed the treated leaves water or 100 mM sucrose for an additional 20 h. Sucrose transport activity was higher than the water ...
Date: August 6, 2002
Creator: Vaughn, Matt; Harrington, Greg & Bush, Daniel R.
Partner: UNT Libraries Government Documents Department