Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 respiration of rabbit heart mitochondria in the presence of ATP is stimulated by ADP, AMP, creatine and glucose plus hexokinase. The values of V for mitochondrial phosphorylating respiration in the presence of corresponding stimulators are equal to 491 +/- 34, 460 +/- 12, 480 +/- 45 and 463 +/- 72 natoms O2 X min-1 X mg-1 of protein, 37 degrees C. The half-maximal stimulation of respiration is observed at 35 microM AMP, 60 microM ADP and 10 mM creatine in the absence of creatine phosphate. In the presence of creatine phosphate the maximal stimulation of heart mitochondrial respiration is achieved under a combined action of creatine and AMP. The inhibition type of mitochondrial respiration by palmitoyl-CoA depends on the nature of stimulators used. Thus, with ADP or glucose plus hexokinase the inhibition is competitive, while with AMP and creatine an uncompetitive and non-competitive inhibition was observed, respectively. The experimental results are indicative of functional coupling of heart mitochondrial adenylate kinase and creatine phosphokinase with ATP-ADP-translocase. It is assumed that creatine and AMP act as physiological regulators of heart mitochondrial respiration ("feed-back" signals from cytoplasm to mitochondria).
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PMID:[Functional coupling of creatine phosphokinase and adenylate kinase with adenine nucleotide translocase and its role in regulation of heart mitochondrial respiration]. 631 78

Skeletal limb muscles of the dog could generally be differentiated into three fibre types according to myosin adenosine triphosphatase (ATPase) (pH 9.4) and succinic dehydrogenase activities. However, because this was not always possible, for comparative purposes only, division into low myosin ATPase (slow twitch) type I and high myosin ATPase (fast twitch) type II fibres was used. The percentage of these fibre types in m deltoideus, m triceps brachii caput longum, m vastus lateralis, m gluteus medius, m biceps femoris and m semitendinosus was examined in the greyhound, crossbred and foxhound. In all muscles the greyhound had a significantly higher percentage of fibres with high myosin ATPase activity at pH 9.4 than the other breeds, with almost 100 per cent in most muscles examined. The activities of nine enzymes and glycogen concentration were determined in m gluteus medius and m semitendinosus of the greyhound and crossbred. Significantly higher levels of creatine kinase, aldolase, alanine aminotransferase and citrate synthase and significantly lower activities of 3-hydroxyacyl coenzyme A dehydrogenase and hexokinase were found in both muscles of the greyhound. The implications of these findings are discussed.
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PMID:Skeletal muscle fibre composition in the dog and its relationship to athletic ability. 645 29

The activities of six different enzymes were compared in 29 normal, 34 dysplastic, and 80 cancerous (both primary and metastatic) human breast tissues; in MCF-7 cells; and in primary rat mammary tumors. Benign lesions generally showed enzyme activities similar to those of normal breast tissues. Malignant tumors had significantly increased activities of lactate dehydrogenase (LDH), malate dehydrogenase (MDH), fructose-bisphosphate aldolase, hexokinase (HK), pyruvate kinase (PK), and creatine kinase. Enzyme activity in the malignant tumor was always higher than that in apparently normal or fibrocystic tissue from the same patient. Enzyme activities did not correlate with the levels of estrogen and progesterone receptors. LDH, MDH, and HK were elevated to a similar extent in all the tissues examined. Conversely, PK was elevated to a much greater extent in cancerous tissues, particularly in MCF-7 cells. The elevated activities of these enzymes may have diagnostic potential, especially when tumor tissue and apparently normal tissue from the same patient are compared.
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PMID:Enzyme activities in normal, dysplastic, and cancerous human breast tissues. 658 10

The enzyme complement of two different mitochondrial preparations from adult rat brain has been studied. One population of mitochondria (synaptic) is prepared by the lysis of synaptosomes, the other (non-synaptic or free) by separation from homogenates. These populations have been prepared from distinct regions of the brain: cortex, striatum, and pons and medulla oblongata. The following enzymes have been measured: pyruvate dehydrogenase (EC 1.2.4.1), citrate synthase (EC 4.1.3.7), NAD-linked isocitrate dehydrogenase (EC 1.1.1.41), NADP-linked isocitrate dehydrogenase (EC 1.1.1.42), fumarase (EC 4.2.1.2), NAD-linked malate dehydrogenase (EC 1.1.1.37), D-3-hydroxybutyrate dehydrogenase (EC 1.1.1.30), and mitochondrially bound hexokinase (EC 2.7.1.1) and creatine kinase (EC 2.7.3.2). The nonsynaptic (free) mitochondria show higher enzyme specific activities in the regions studied than the corresponding values recorded for the synaptic mitochondria. The significance of these observations is discussed in the light of the different metabolic activities of the two populations of mitochondria and the compartmentation of the metabolic activities of the brain.
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PMID:The activities of some energy-metabolising enzymes in nonsynaptic (free) and synaptic mitochondria derived from selected brain regions. 670 35

The utilization of isocratic, reverse-phase, ion-paired high-performance liquid chromatography for analysis of creatine phosphate allows for rapid quantification of multiple samples. Cryogenic sample handling and the addition of ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid as a Ca2+ sequestering agent during perchloric acid extraction enhance maximal recovery of creatine phosphate from brain samples. Peak identification is supported by a complete enzymatic shift with a phosphocreatine kinase, hexokinase, and glucose-6-phosphate dehydrogenase system.
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PMID:Determination of creatine phosphate levels in brain tissue by isocratic reverse-phase, ion-paired high-performance liquid chromatography. 673 48

Further studies of mitochondrially bound hexokinase have been carried out in order to elucidate the mechanism first proposed to increase efficiency of oxidative phosphorylation by the acceptor effect (Bessman, S. P. (1954) in Fat Metabolism (Najjar, V., ed) pp. 133-137, Johns Hopkins Press, Baltimore). During isolation of mitochondria, Mg2+ caused increased quantities of hexokinase to be bound or retained. This effect is concentration-dependent, saturable, and cannot be explained by Mg2+-linked activation or stabilization. Rebinding of hexokinase to isolated mitochondria also shows a similar dependence on Mg2+. When added to a homogenate made without it, Mg2+ could not bind the same amount of hexokinase to the mitochondria as could be observed when Mg2+ had been included in the homogenizing medium from the start. Using mitochondria prepared with Mg2+ in order to bind hexokinase to the largest extent possible, we have demonstrated that as in the case of mitochondrial creatine phosphokinase, a compartment exists that permits more efficient production of glucose 6-phosphate during mitochondrial respiration--the hexokinase acceptor effect. This effect probably results from a favorable positioning of the active site of hexokinase, perhaps within the intermembrane space, providing a diffusion-favorable situation. Thus, newly synthesized ATP transported through the inner membrane supplies substrate to hexokinase with greater efficiency than that of ATP which must pass through the outer membrane by diffusion from the medium. These observations lend support to proposals that in vivo modulation of the soluble particulate distribution of hexokinase by hormones or by metabolites may be physiologically necessary and important.
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PMID:Evidence for functional hexokinase compartmentation in rat skeletal muscle mitochondria. 674 64

Muscle biopsies were obtained from three cyclists and four runners at the end of 10-24 mo of intensive training and after intervals of detraining up to 12 wk. Control samples came from four untrained persons and four former athletes. Macro mixed fiber samples were assayed for lactate dehydrogenase, adenylate kinase, glycogen phosphorylase, citrate synthase, malate dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, creatine kinase, hexokinase, 1-phosphofructokinase, fructosebisphosphatase, protein, and total creatine. In the case of three trained persons and two controls, the first six of the enzymes were also measured in individual fibers. Before detraining, enzymes of oxidative metabolism were substantially higher than in controls, and differences in levels between type I and type II fibers were smaller. During detraining, oxidative enzymes were decreased in both fiber types but the type II fibers did not fall to control levels even after 12 wk. Phosphorylase increased with detraining in both fiber types. The same is true for lactate dehydrogenase and adenylate kinase, except in the case of the type I fibers of one individual. Among the other six enzymes (measured in mixed fiber samples), only hexokinase was consistently affected (decreased) by detraining.
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PMID:Effects of detraining on enzymes of energy metabolism in individual human muscle fibers. 682 50

In 13 rabbits the rectus femoris muscle was freely transplanted from the left to the right side using microneurovascular anastomoses. About 7 months after surgery the muscle transplants were assessed functionally by force measurements. On the average, the transplanted muscles regained 55 percent of the maximal tetanic tension of unoperated, normal rectus femoris muscles, expressed as force per gram of muscle weight even 68 percent. After functional assessment, the muscles were weighed and then used for histologic, histochemical, planimetric, and biochemical evaluation. H&E-stained cross sections showed a high content of healthy muscle fibers; only some small atrophic and single fat cells were scattered over the cross sections. Good reinnervation over the sutured muscle nerve was confirmed by the type-grouping of muscle fibers in the NADH and myofibrillar ATPase staining. There was an excellent correlation between the functional results and the histologic picture as well as the content of choline acetyltransferase (CAT). A certain parallelism was found between the function of the transplants and the content of hexokinase, but none for the other estimated muscle enzymes, such as malate dehydrogenase (MDH), creatine kinase (CK), and lactic dehydrogenase (LDH). All enzyme levels were lower than in normal muscles. The results of this experimental series underline the utility of muscle transplantation with microneurovascular anastomoses to restore lost muscle function, even in the extremities, when strong forces are needed.
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PMID:Experimental free-muscle transplantation with microneurovascular anastomoses. 683 65

Mitochondrial creatine kinase was first proposed to act as a functional component in respiratory control in 1966 (Bessman, S. P., and Fonyo, A. (1966) Biochem. Biophys. Res. Commun. 22, 597-602). Since that time, evidence has accumulated to support the theory of a creatine-phosphorylcreatine shuttle mechanism involved in supplying energy for aerobic muscle contraction (Bessman, S. P., and Geiger, P. J. (1981) Science 211, 448-452). To demonstrate directly the interaction between mitochondrial oxidative phosphorylation and that of creatine phosphate synthesis, we have studied the labeling of adenine nucleotides and creatine phosphate with [33P]H3PO4 or [gamma-32P]ATP over a range of adenine nucleotide concentrations incubated with rabbit cardiac and rat skeletal muscle mitochondria. An apparent direct mitochondrial ATP contribution to creatine phosphate synthesis was observed that varied inversely with the total adenine nucleotide present in the reaction system. This reaction of de novo synthesized ATP with creatine phosphokinase prior to equilibration with the total ATP pool was observed regardless of the entry point of electrons from oxidizable substrate into the electron transport chain. This special relation was not observed for added yeast hexokinase in forming glucose 6-phosphate. Mitochondria could not synthesize creatine phosphate in the presence of atractyloside, thus underscoring the requirement for adenine nucleotide translocase-linked transport of ATP prior to reaction with the bound creatine phosphokinase. These studies show that there is coupling or compartmentation of ATP synthesis and transport with creatine phosphate formation in heart and skeletal muscle mitochondria.
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PMID:Compartmentation of mitochondrial creatine phosphokinase. I. Direct demonstration of compartmentation with the use of labeled precursors. 714 17

Interpretation of biochemical measurements in the human brain after death is complicated by a variety of premortem, perimortem, and postmortem factors. The activity of glutamic acid decarboxylase (GAD) in particular has been found to vary considerably among human brains. In contrast to neurotransmitter-associated enzymes, metabolic enzymes are present in all brain cells and should not be specifically lost by patterned neuronal cell loss such as that which occurs in Parkinson disease. We compared the activity of GAD to that of the metabolic enzymes creatine kinase (CK), adenylate kinase, hexokinase, beta-glucuronidase, and malate, lactate, glucose-6-phosphate, and isocitrate dehydrogenases in 24 regions of six human brains. Of the metabolic enzymes, only CK showed a 5-fold variation approaching that of GAD. Like GAD, CK activity was stable postmortem, but its activity was apparently inversely related to the severity and duration of the preterminal illness. CK may be a useful marker of agonal deterioration.
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PMID:Regional activities of metabolic enzymes and glutamate decarboxylase in human brain. 731 90


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