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

In the subcommissural organ (SCO) of the guinea pig, rat, golden hamster, and mouse the activity and distribution of enzymes related to the energy-supplying metabolism and of some marker enzymes of different cell organelles have been investigated by means of mostly modified histochemical methods. The results were compared with findings in the ciliated ependyma of the ventricular wall and with those in the ependyma of the choroid plexus of the third ventricle. In the ependymal part of the SCO only a moderate activity of hexokinase is observed in its specialized columnar cells whereas a high activity is present both in the ciliated ependyma and the choroid plexus. - The staining pattern of glucose-6-phosphatase is similar to that of hexokinase but this enzyme is found is the SCO only. - Likewise hexokinase, glycogen granules and enzymes related to glycogen metabolism (phosphoglucomutase, uridine-diphosphoglucose pyrophosphorylase, glycogen synthetase and phosphorylase) are regularly found most numerous and active in the nuclear and supra-nuclear area of the ependymal part. These enzymes are less active in both the other ependymal regions. - Uridine-diphosphoglucose dehydrogenase could not be demonstrated in the SCO. The NADP-linked enzymes of the pentose phosphate shunt, glucose-6-phosphate and 6-phosphogluconate dehydrogenase, show a moderate activity which decreases also from the nuclear towards the apical area of the ependymal cells of the SCO. Enzymes of the glycolytic pathway, such as glucosephosphate isomerase, fructose-6-phosphate kinase, fructose-I,6-diphosphate aldolase, glyceraldehyde-3-phosphate and lactate dehydrogenase, are highly active in the SCO and are located mainly in the supranuclear area, too. Fructose-1,6-diphosphatase could not be demonstrated thus indicating that in the SCO the pathway is most probably only glycolytic but not gluconeogenetic. Compared to the ependyma of the ventricular wall and of the choroid plexus, in the SCO the M type subunits of lactate dehydrogenase predominate. Glycolytic enzymes are also very active in the choroid plexus but less in the ciliated ependyma. Compared to the ciliated ependyma and especially to the ependyma of the choroid plexus, the activities of enzymes which are only present in mitochondria (NAD-linked isocitrate dehydrogenase, succinate dehydrogenase, NAD-linked malate dehydrogenase after preextraction, cytochrome oxidase, 3-hydroxybutyrate and glycerolphosphate and glutamate dehydrogenase) are relatively low. Mitochondria are accumulated near the superior pole of the nuclei as well as in the most apical part of the ependymal cells. - The staining pattern of NADP-linked isocitrate and malate dehydrogenase as well as of NADH dehydrogenase suggests that these enzymes are localized both in and out of mitochondria. The extramitochondrial activity of the first two enzymes might be localized in the cytosol. The extramitochondrial activity of NADH dehydrogenase might be localized in the endoplasmic reticulum...
 ...
PMID:Enzymatic organization of the subcommissural organ. 123 49

The consumption of glucose by trypanosomatid protozoa such as Trypanosoma brucei, Trypanosoma cruzi, Leishmania spp., and Crithidia spp. is characterized by the excretion of reduced products such as succinate, pyruvate, ethanol, L-alanine, or lactate (depending on the species) not only in anaerobiosis, but also under aerobic conditions. The "aerobic fermentation" of glucose is accompanied by a complete lack, or even a reversal, of the Pasteur effect. This peculiar catabolism is mediated by a so-far unique compartmentation of the glycolytic enzymes, most of which are placed in an organelle called the glycosome; by an almost complete lack of inhibitory controls at the level of hexokinase and phosphofructokinase; and by a central role of CO2 fixation through the reaction catalyzed by phosphoenolpyruvate carboxykinase. The production of fermentative products seems to be due to a relative inefficiency of the respiratory chain, which lacks NADH dehydrogenase and the first phosphorylation site and preferentially uses succinate as substrate.
 ...
PMID:Aerobic fermentation of glucose by trypanosomatids. 139 37

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
 ...
PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7

The energy metabolism of the English E-CMO strain of contagious equine metritis bacterium was studied in whole cells and cell extracts. This bacterium appears to have an active Krebs cycle and probably obtains energy by oxidative phosphorylation since glycolysis and the hexose monophosphate pathways appear to be absent. These conclusions are based on the findings that [U-14C]glucose incorporation by this bacterium is below the level of detection, and that respiration is stimulated by Krebs cycle intermediates (i.e., malate, citrate, and succinate), but not by glucose, fructose, maltose, or sucrose. Furthermore, support comes from the fact that enzymes generally associated with the Krebs cycle and electron transport (i.e., malate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase, fumarate hydratase, malate dehydrogenase [decarboxylating], cytochrome oxidase, superoxide dismutase, NADH dehydrogenase, and catalase) were detected. Those enzymes normally associated with glycolysis and the hexose monophosphate pathways (i.e., hexokinase, glucose 6-phosphate dehydrogenase, fructose biphosphate aldolase, glycerol 3-phosphate dehydrogenase, phosphoenolpyruvate carboxykinase, pyruvate kinase, phosphate acetyl transferase, acetate kinase, alcohol dehydrogenase, and lactate dehydrogenase) were below the level of detection.
 ...
PMID:Energy metabolism of the contagious equine metritis bacterium. 708 71

Physiological increases in matrix calcium are known to stimulate three mitochondrial dehydrogenases. In mitochondria isolated from rat heart, calcium stimulates rates of State 3 respiration during oxidation of succinate and of several NAD-linked substrates. In this study, we investigated the effects of calcium on NADH dehydrogenase and succinate dehydrogenase activities since the mechanism of these effects is unresolved. The respiratory activities of intact mitochondria and submitochondrial particles (SMP) were compared during incubation in media containing either ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) or a Ca2+/EGTA buffer (approximately 1 microM free Ca2+). In intact mitochondria oxidizing 20 mM glutamate plus 2 mM malate, the membrane potential (delta psi) and matrix NAD(P)H were maintained at higher levels, and the maximal rate of ADP-stimulated respiration (State 3) was increased twofold by the presence of calcium. With succinate as substrate, calcium stimulated State 3 respiration but it did not influence the pyridine nucleotides redox state or membrane potential. Stimulation of succinate-supported respiration by addition of 6-10 microM ADP in the presence of hexokinase caused a sudden decrease in NAD(P)H and collapse of delta psi. This effect was not caused by inhibition of succinate dehydrogenase or by opening of the nonspecific pore. Calcium did not influence the oxidation of succinate by SMP containing either activated or nonactivated succinate dehydrogenase. In addition, calcium did not alter the kinetics of succinate dehydrogenase activation. Calcium and magnesium, in the concentration range of 0.02 to 5 mM, did not influence the NADH dehydrogenase activity of SMP. Energization of SMP by oligomycin addition, however, dramatically influenced the kinetic properties of NADH dehydrogenase. It is proposed that in heart mitochondria, calcium does not affect directly the components of electron transport but it may influence the activity of NADH dehydrogenase indirectly by increasing delta psi.
 ...
PMID:Influence of calcium on NADH and succinate oxidation by rat heart submitochondrial particles. 786 38