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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutants with defective carbon catabolite repression have been isolated in the yeast Saccharomyces cerevisiae using a selective procedure. This was based on the fact that invertase is a glucose repressible cell wall enzyme which slowly hydrolyses raffinose to yield fructose and that the inhibitory effects of 2-deoxyglucose can be counteracted by fructose. Repressed cells were plated on a raffinose--2-doexyglucose medium and the resistant cells growing up into colonies were tested for glucose non-repressible invertase and maltase. The yield of regulatory mutants was very high. All were equally derepressed for invertase and maltase, no mutants were obtained with only non-repressible invertase synthesis which was the selected function. A total of 61 mutants isolated in different strains were allele tested and could be attributed to three genes. They were all recessive. Mutants in one gene had reduced hexokinase activities, the other class, located in a centromere linked gene, had elevated hexokinase levels and was inhibited by maltose. Mutants in a third gene were isolated on a 2-deoxyglucose galactose medium and had normal hexokinase levels. A partial derepression was observed for malate dehydrogenase in all mutants. Isocitrate lyase, however, was still fully repressible.
Mol Gen Genet 1977 Jul 07
PMID:Mutants of Saccharomyces cerevisiae resistant to carbon catabolite repression. 19 90

Several characteristics of the binding of insulin and glucagon to human circulating mononuclear leukocytes have been studied. Functional analysis (latex bead ingestion) revealed that cell mixtures, as prepared according to Boyum and used generally in studies of insulin resistance in humans, consist of 20-29% phagocytic monocytes, with the remainder being lymphocytes. Partial separation of monocytes from lymphocytes on columns of Sephadex G-10, followed by correlation of insulin binding with cell type, confirms that the monocyte is the binding species. Insulin influenced neither glucose uptake nor the further conversion of glucose to lipids and CO2 by the leukocytes. The transport of alpha-aminoisobutyrate, a nonmetabolizable amino acid, into these cells was also unaffected by insulin. Monocyte/lymphocyte mixtures specifically bound glucagon and prostaglandin E1. At physiological concentrations of these hormones, steady states were reached in 15 min and 45 min, respectively. In contrast to the 8-10-fold increases in cellular cyclic AMP produced by prostaglandins, the effect of glucagon was very small but apparently real. Under appropriate preincubation conditions, sodium azide and iodoacetamide inhibited phagocytosis and insulin binding in parallel. The binding of glucagon was unaffected by these agents. Although both antimycin A and actinomycin D inhibited phagocytosis of the monocytes, only the former inhibited insulin binding; there was only a slight effect on glucagon binding. We would conclude that the binding of insulin to human circulating monocytes, although reflective of insulin resistance in diabetes mellitus and obesity, may not be to traditional receptors. In contrast, the binding of glucagon to lymphocyte/monocyte mixtures may be to function-linked receptors.
Mol Cell Endocrinol 1977 Oct
PMID:Hormone receptors: VI. On the nature of the binding of glucagon and insulin to human circulating mononuclear leukocytes. 20 May 11

The splanchnic-hepatic metabolism of glucose, lactate, pyruvate, alanine, glycerol, non-esterified fatty acids (NEFA), ketone bodies and oxygen were investigated in five normal men and six juvenile diabetic subjects at rest and during exercise after an overnight fast. A linear relationship was found between load (arterial concentration multiplied by hepatic blood flow) and splanchnic-hepatic uptake of lactate, pyruvate, glycerol and NEFA. The uptake of alanine was highly sensitive to load, but was also regulated by the concentration of hepatic venous glucagon. The uptake of pyruvate was high in exercising diabetic subjects, who had a high lactate/pyruvate concentration ratio in hepatic venous blood. The rate of uptake of the total measured gluconeogenic precursors was significantly higher in the diabetic group at a given load. The rate of ketogenesis was linearly related to the NEFA load in both groups; however, the rate of ketogenesis was twofold at a given load in the diabetic group. The highest rates of ketogenesis were found coincident with the highest concentrations of glucagon in hepatic venous blood. The observed antiketogenic effect of exercise was due to a decreased load of NEFA, mainly caused by a decrease in the hepatic blood flow.
Clin Sci Mol Med 1977 Nov
PMID:Regulation of gluconeogenesis and ketogenesis during rest and exercise in diabetic subjects and normal men. 20 21

Glucose represses mitochondrial biogenesis and the fermentation of maltose, galactose and sucrose in yeast. We have analyzed the effect of D-glucosamine on these functions in order to determine if it can produce a similar repression. It was found that glucosamine represses the respiration rate (QO2) but more rapidly than glucose and to a final level slightly higher than in glucose-treated cells. Derepression of the respiration rate following either glucose or glucosamine repression was similar. A two hour lag was followed by a linear increase in QO2 to the derepressed level. Both glucose and glucosamine repressed the level of cytochrome oxidase to the same level. Glucosamine was also found to repress maltose and galactose fermentation but not sucrose fermentation. The derepression of maltase synthesis was inhibited by glucosamine. The constitutive synthesis of maltase was repressed by the addition of glucosamine. Glucosamine was judged to produce a repressed state similar to glucose repression in many respects.
Mol Gen Genet 1977 Oct 24
PMID:An evaluation of D-glucosamine as a gratuitous catabolite repressor of Saccharomyces carlsbergensis. 20 60

HTC cells are able to convert alpha-linolenic acid into higher homologs by desaturating and elongating reactions. When the cells were cultured in a Krebs Ringer bicarbonate solution ("fasted cells") a decrease in both biosynthetic reactions took place. "Refeeding" the cells with Swim's 77 medium without glucose enhanced the biosynthesis of polyunsaturated fatty acids from alpa-linolenic acid family, but when glucose was added to the medium, alpha-linolenic acid was preferably elongated rather than converted into eicose-pentaenoic acid. The ultrastructural study revealed HTC cells with a simple cytoplasmic organization, showing little evidence of their origin from hepatocytes. The cells cultured in a complete medium appeared well preserved and were similar to those "fasted" for 12 hours and "refed" for another 12 hours using Swim's 77 medium without serum. The amount of glucose in the medium plays a role in preserving the cell structure. This effect does not occur if glucose is added in the absence of aminoacids and vitamins.
Mol Cell Biochem 1977 Nov 25
PMID:Effect of "fasting" and different concentrations of glucose on alpha-linolenic acid metabolism in HTC cells. Correlation with the ultrastructural study. 20 61

Yeast mutants with glucose-insensitive formation of mitochondrial enzymes were isolated starting with a strain completely lacking alcohol dehydrogenase activity. The mutations could uniquely be attributed to a single nuclear gene, designated CCR80. They were largely dominant. Glucose-resistant enzyme formation was most prominent with regard to mitochondrial enzymes succinate dehydrogenase and NADH: cytochrome c oxidoreductase. The effect of CCR80r mutations was rather small but significant on the gluconeogenetic enzymes isocitrate lyase, malate synthase and fructose-1,6-bisphosphatase and on invertase synthesis. The repressive effect of maltose in CCR80r mutants was also reduced showing that glucose-resistance is not caused by a mere hexose uptake defect. This regulatory disorders were not accompanied by reduced levels of glycolytic enzymes or drastically altered levels of glycolytic intermediates. Aerobic fermentation of glucose was almost completely inhibited in the mutants; anaerobic glucose degradation was reduced but not completely abolished. Therefore, the mutants appear to be altered in the regulation of glycolysis. A largely glucose-resistant synthesis of respiratory enzymes is obviously a corollary of this alteration.
Mol Gen Genet 1978 Feb 27
PMID:A yeast mutant with glucose-resistant formation of mitochondrial enzymes. 20 62

Using a mathematical model of carbohydrate metabolism in Dictyostelium discoideum, the kinetic expressions describing the activities of glucokinase and glucose-6-P phosphatase have been analyzed. The constraints on the kinetic mechanisms and relative activities of these two enzymes were investigated by comparing computer simulations to experimental data. The results indicated that, (1) glucose-6-P is compartmentalized with respect to the enzymes involved in glucose-60P, trehalose and glycogen metabolism, (2) a differences of approximately 0.6 mM/min in maximum specific activity of glucokinase compared to glucose-6-P phosphatase is required in order for the model to produce end product carbohydrate levels consistent with those observed experimentally, (3) the Km of glucokinase for glucose strongly influences the steady state levels of glucose in the absence of external glucose, and (4) changing the order of product removal in the reaction catalyzed by glucose-6-P phosphatase influences the level of glycogen and trehalose.
Mol Cell Biochem 1978 Apr 11
PMID:A kinetic analysis of glucokinase and glucose-6-P phosphatase in Dictyostelium. 20 18

The rapid isolation of high yields of parenchymal cells from chicken liver is described. Stringent tests of viability show that the isolated hepatocytes are both structurally and metabolically similar to those in intact liver. During incubation viability decreased and the significance of this change on the interpretation of metabolic experiments is discussed. Lactate was a much more effective gluconeogenic precursor than pyruvate even in the presence of additional reducing equivalents. Hepatocytes isolated from fed chickens produced glucose from glycogen degradation. Glycogenolysis was stimulated by glucagon, dibutyryl cyclic AMP and adrenaline. Half maximal glucagon effects were elicited by physiological concentrations of the hormone. Glucagon and dibutyryl cyclic AMP stimulated glucagon, dibutyryl cyclic AMP and adrenaline their action was not additive to that of adrenaline.
Mol Cell Biochem 1978 Apr 11
PMID:The use of viable hepatocytes to study the hormonal control of glycogenolysis in the chicken. 20 19

Based on previous studies which have revealed that glucose 1,6-bisphosphate (Glc-1,6-P2) is a potent inhibitor of muscle hexokinase and an activator (deinhibitor) of phosphofructokinase and phosphoglucomutase, the effect of epinephrine on the levels of this regulator in rat diaphragm muscle was investigated. It was found that epinephrine caused an increase in diaphragm Glc-1,6-P2 levels, accompanied by a reduction in the activity of hexokinase and an activation (deinhibition) of phosphofructokinase and phosphoglucomutase. N6-2'-O-dibutyryl cyclic AMP was able to mimic all these effects of epinephrine. The concentration of glucose-6-phosphate was not changed by epinephrine, under conditions in which the hormone produced an increase in cyclic AMP and Glc-1,6-P2 levels and the concomitant decrease in hexokinase activity. It was also shown that Glc-1,6-P, in the concentration range found after epinephrine, inhibited the diaphragm hexokinase and deinhibited phosphoglucomutase. These results may suggest a mechanism of epinephrine action by which the activities of hexokinase, phosphoglucomutase and phosphofructokinase, through the action of Glc-1,6-P2, are synchronized with the cyclic AMP-mediated activation of glycogen phosphorylase, to achieve an increase in total glycogenolysis and glycolysis and a concomitant reduction in glucose utilization by the muscle.
Mol Cell Endocrinol 1978 Apr
PMID:The effect of epinephrine and dibutyryl cyclic AMP on glucose 1,6-bisphosphate levels and the activities of hexokinase, phosphofructokinase and phosphoglucomutase in the isolated rat diaphragm. 20 4

The insulinotropic effects of alpha-ketoisocaproic acid and glucose reveal many common characteristics in vivo and in vitro. They qualify as initiators of insulin release, their action is amplified by potentiators of insulin release, and they have a similar potency at equimolar concentrations. The dynamics of insulin release evoked by alpha-ketoisocaproic acid and glucose are similar. Epinephrine completely inhibits the insulinotropic effect of glucose and alpha-ketoisocaproic acid. Mannoheptulose exhibits a complete, immediate and reversible blockade of glucose-induced insulin release. In contrast, inhibition of alpha-ketoisocaproic acid-induced insulin release occurs after a lag period and is not reversed by removal of the inhibitor. alpha-ketoisocaproic acid, at equimolar concentrations, is several-fold more effective than glucose in elevating cAMP content in islet. alpha ketoisocaproic acid and glucose are about equally effective in stimulating somatostatin release from isolated rat pancreatic islets. This stimulation is inhibited by epinephrine. Mannoheptulose inhibits only somatostatin release induced by glucose but not by alpha-ketoisocaproic acid. It suggested that the insulinotropic characteristics of glucose and alpha-ketoisocaproic acid reveal many common features, while their mode of action appears to be different.
Mol Cell Endocrinol 1978 Jun
PMID:Comparison of alpha-ketoisocaproic acid and glucose in rats: effects on insulin and somatostatin release and on islet cAMP content. 21 60


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