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)

Evidence is presented for the occurrence of glycosomes (organelles resembling peroxisomes) in four major species of Leishmania (viz. L. major, L.m. mexicana, L. b. braziliensis and L. donovani), based on latency as well as differential and isopycnic centrifugation studies. The enzymes involved in glycolysis; (hexokinase, phosphoglucose isomerase, phosphofructokinase, fructose-1,6-bisphosphate aldolase, triosephosphate isomerase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase); glycerol metabolism (sn-glycerol-3-phosphate dehydrogenase and glycerol kinase); carbon dioxide fixation (phosphoenolpyruvate carboxykinase and possibly malate dehydrogenase); together with an enzyme involved in the beta-oxidation of fatty acids (3-beta-hydroxybutyryl coenzyme A dehydrogenase); a key enzyme in the synthesis of ether lipids (dihydroxyacetone phosphate acyltransferase) as well as the ADP utilising enzyme adenylate kinase, were all found associated, at least in part, with a subcellular organelle which had a buoyant density in sucrose gradients of 1.21 to 1.24 g cm-3. Little variance in enzyme composition was found between the different species of Leishmania or in comparison with other members of the Trypanosomatidae, supporting the unifying principle that glycosomes are a unique characteristic of this family. The occurrence of important catabolic, anabolic and anaplerotic pathways in the glycosomes of Leishmania renders them prime targets for chemotherapy.
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PMID:The occurrence of glycosomes (microbodies) in the promastigote stage of four major Leishmania species. 644 18

A method is presented for the simultaneous purification of hexokinase, fructose-bisphosphate aldolase, triosephosphate isomerase and phosphoglycerate kinase, and the partial purification of glycerol-3-phosphate dehydrogenase (NAD+), 6-phosphofructokinase, glucosephosphate isomerase, and glycerol kinase from Trypanosoma brucei. As a first step, the glycosomes, microbody-like organelles of Trypanosomatidae, containing almost exclusively enzymes involved in glucose and glycerol metabolism [Opperdoes, F. R. and Borst, P. (1977) FEBS Lett. 80, 360-364], were purified eightfold from homogenates with an average yield of 38%. Subsequently, the glycosomal content was subjected to hydrophobic interaction chromatography on phenyl-Sepharose. This step results in pure hexokinase (15% final yield) and almost pure triosephosphate isomerase, while the other glycosomal enzymes elute as mixtures of two or three enzymes. Triosephosphate isomerase was further purified to homogeneity on CM-cellulose (33% final yield), while phosphoglycerate kinase and fructose-bisphosphate aldolase were separated from each other and purified to homogeneity by affinity chromatography using ATP-Sepharose (25% and 30% final yields, respectively). Fructose-bisphosphate aldolase was further characterized as a typical class I enzyme.
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PMID:Simultaneous purification of hexokinase, class-I fructose-bisphosphate aldolase, triosephosphate isomerase and phosphoglycerate kinase from Trypanosoma brucei. 648 38

Procyclic culture forms of Trypanosoma brucei stock 427 have been screened for the presence of enzymes involved in glycolysis, mitochondrial energy metabolism and threonine degradation. The enzyme activities in the procyclics were compared with those of the blood stream forms. The specific activities of glycolytic enzymes represented 30-70% of the respective levels in the blood stream form, except for hexokinase which was 25-fold reduced. Cell fractionation showed that the enzymes involved in the early sequence of the glycolytic pathway, i.e. from hexokinase to phosphoglycerate kinase, and the enzymes NAD+-linked glycerol-3-phosphate dehydrogenase and glycerol kinase were all present in glycosomes equilibrating at a density of 1.23 g/cm3 in sucrose gradients. Malate dehydrogenase was 8-fold more active in procyclics than in bloodstream forms. This increase in activity was the result of the appearance of malate dehydrogenase in the glycosomes of the procyclics, in addition to mitochondrial and cell-sap activities which were present in both stages of the life cycle. Glycosomes contained part of the adenylate kinase activity, which was also associated with the mitochondrion. Succinate dehydrogenase and sn-glycerol-3-phosphate dehydrogenase, together with oligomycin-sensitive ATPase, were located in the mitochondrion which had a density in sucrose ranging from 1.16 to 1.18 g/cm3. This organelle also contained L-threonine 3-dehydrogenase and carnitine acetyltransferase, two enzymes involved in threonine catabolism. The latter two enzymes had activities which were, respectively, 15-and 13-fold higher in the procyclics than in the bloodstream form. Mitochondrial sn-glycerol-3-phosphate dehydrogenase was decreased 4-fold.
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PMID:Localization of malate dehydrogenase, adenylate kinase and glycolytic enzymes in glycosomes and the threonine pathway in the mitochondrion of cultured procyclic trypomastigotes of Trypanosoma brucei. 680 9

The voltage-dependent anion channel of the mitochondrial outer membrane (VDAC) is a small, abundant pore-forming protein found in the outer membranes of all eukaryotic mitochondria. The VDAC protein is believed to form the major pathway for movement of adenine nucleotides through the outer membrane and to be the mitochondrial binding site for hexokinase and glycerol kinase. Previous studies have indicated that at least two human VDAC isoforms are expressed. Here, we report the mapping of VDAC1 to the X chromosome in the interval Xq13-q21 and VDAC2 to chromosome 21 by polymerase chain reaction and restriction analysis of a human/rodent somatic cell mapping panel. In the process of mapping these genes, we identified and mapped two additional sequences highly homologous to VDAC1. VDAC3 maps to chromosome 12 and VDAC4 maps to chromosome 1. The locations of VDAC1 and VDAC4 have been confirmed by fluorescence in situ hybridization analysis. Future studies will be aimed at defining the specific physiological role of each member of this family of channel proteins.
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PMID:Human genes encoding the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane: mapping and identification of two new isoforms. 751 85

X-ray structure analysis of actin and of the NH2-terminal domain of the heat-shock cognate protein Hsc70 has revealed an unexpected extensive structural similarity between these two molecules. Despite the absence of significant similarity of their amino acid sequences, both proteins share the same core architecture and a common nucleotide binding site resembling the structure of hexokinase. All three are ATPases or kinases and bind ATP in association with Mg2+ or Ca2+. The common fold consists of two alpha/beta domains, which are connected by a putative hinge with an ATP-binding site situated between the domains. Each domain contains a five-stranded beta-sheet of identical topology, which suggests that the molecules may have evolved by gene duplication. From a comparison of the three aligned structures, a fingerprint sequence of the adenine nucleotide binding pocket was derived, which predicted that members of the glycerol kinase family should also have a similar fold of their nucleotide binding domain. This was later confirmed when the X-ray structure was published. Data base search with a refined consensus sequence has retrieved other sugar kinases, as well as the prokaryotic cell cycle proteins FtsA, MreB, and StbA, and two Escherichia coli phosphatases. These proteins are predicted to possess a structure similar to actin in the common core region. As exemplified for actin, Hsc70, and glycerol kinase, the diversity of biological function is provided by the polymorphism of the loops joining the beta-strands and helices in the core region and by inserted domains that show high variability.
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PMID:The actin fold. 778 19

Complexes made up of the kinases, hexokinase and glycerol kinase, together with the outer mitochondrial membrane voltage-dependent anion channel (VDAC) protein, porin, and the inner mitochondrial membrane protein, the adenine nucleotide translocator, are involved in tumorigenesis, diabetes mellitus, and central nervous system function. Identification of these two mitochondrial membrane proteins, along with an 18 kD protein, as components of the peripheral benzodiazepine receptor, provides independent confirmation of the interaction of porin and the adenine nucleotide translocator to form functional contact sites between the inner and outer mitochondrial membranes. We suggest that these are dynamic structures, with channel conductances altered by the presence of ATP, and that ligand-mediated conformational changes in the porin-adenine nucleotide translocator complexes may be a general mechanism in signal transduction.
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PMID:Microcompartmentation of energy metabolism at the outer mitochondrial membrane: role in diabetes mellitus and other diseases. 807 85

The binding of hexo-/glucokinase and glycerol kinase to mitochondria via the channel forming protein, porin, in pancreatic islet beta-cells and adipocytes, was recently proposed to participate in nutritional signaling, glucose sensing, and the control of high-energy phosphate distribution and oxidative phosphorylation. In this study we demonstrate that polyclonal antisera against purified rat liver porin recognize unique proteins in rat pancreatic islets, adipocytes, and RINm5F cells, each with an apparent M(r) about 2000 smaller than that of liver porin. Immunoblotting of subcellular fractions, the purity of which has been controlled by the distribution of marker proteins, revealed the mitochondrial localization of the cross-reacting proteins. Their enrichment with a method used for the purification of porin proteins, the characteristic behavior during isoelectric focusing, and the specific binding of rat liver hexokinase and glycerol kinase to phospholipid vesicles containing the purified cross-reacting beta-cell or adipocyte proteins strongly suggest their identity with mitochondrial porin. The subtle differences in the apparent M(r) and charge heterogeneity raise the possibility of the existence of porin isoforms expressed in a tissue-specific manner. Anti-porin antisera coimmunoprecipitated hexo-/glucokinase from rat insulinoma cell (RINm5F) and adipocyte mitochondria as determined by subsequent immunoblotting of the immunoprecipitates with polyclonal antisera against yeast hexokinase and rat liver glucokinase, respectively. This indicates that some rat pancreatic glucokinase (54 kDa) and liver hexokinase (102 kDa), respectively, is bound to mitochondrial porin. The major portion of the bound fraction is released from mitochondria after treatment with glucose 6-phosphate. Incubation of RINm5F and fat cells with the insulin releasing sulfonylurea drug, glimepiride (20 nM and 5 microM, respectively) for 30 min reduces the amount of hexo-/glucokinase associated with mitochondria and porin to about 50-30%. The reduced kinase binding activity of porin is preserved after isolation of porin from glimepiride-treated cells, reconstitution into phospholipid vesicles and assaying for glucose 6-phosphate inhibitable binding of rat liver hexokinase. The sulfonylurea tolbutamide (20 microM and 5 mM) is significantly less effective. The sulfonylurea-induced inhibition of hexo-/glucokinase binding to mitochondrial porin does not require glucose metabolism or Ca2+ influx into the cells. These data suggest that the sulfonylurea glimepiride, which is thought to inhibit the ATP-regulated K(+)-channel in beta-cells, may have, in addition, an intracellular site of action in pancreatic islet and adipocyte cells at the level of regulation of gluco-/hexokinase binding to mitochondrial porin.
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PMID:Porin proteins in mitochondria from rat pancreatic islet cells and white adipocytes: identification and regulation of hexokinase binding by the sulfonylurea glimepiride. 831 78

The voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane is a small abundant protein found in all eukaryotic kingdoms which forms a voltage-gated pore when incorporated into planar lipid bilayers. VDAC is also the site of binding of the metabolic enzymes hexokinase and glycerol kinase to the mitochondrion in what may be a significant metabolic regulatory interaction. Recently, there has been speculation that there may be multiple forms of VDAC in mammals which differ in their localization in the outer mitochondrial membrane and in their physiological function. In this report, we describe the identification and characterization of two human cDNAs encoding VDAC homologs (HVDAC1 and HVDAC2). To confirm VDAC function, each human protein has been expressed in yeast lacking the endogenous VDAC gene. Human proteins isolated from yeast mitochondria formed channels with the characteristics expected of VDAC when incorporated into planar lipid bilayers. In addition, expression of the human proteins in such strains can complement phenotypic defects associated with elimination of the endogenous yeast VDAC gene. Since VDAC is the site of binding of hexokinase to the outer mitochondrial membrane, the binding capacity of each VDAC isoform expressed in yeast mitochondria was assessed. When compared with the binding of hexokinase to mitochondria lacking VDAC, the results show that mitochondria expressing HVDAC1 are capable of specifically binding hexokinase, whereas mitochondria expressing HVDAC2 only bind hexokinase at background levels. The expression of each human cDNA has been assessed by Northern blot and polymerase chain reaction techniques. With one exception, each is expressed in all human cell lines and tissues examined.
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PMID:Cloning and functional expression in yeast of two human isoforms of the outer mitochondrial membrane channel, the voltage-dependent anion channel. 842 Sep 59

The phosphocarrier protein IIIGlc is an integral component of the bacterial phosphotransferase (PTS) system. Unphosphorylated IIIGlc inhibits non-PTS carbohydrate transport systems by binding to diverse target proteins. The crystal structure at 2.6 A resolution of one of the targets, glycerol kinase (GK), in complex with unphosphorylated IIIGlc, glycerol, and adenosine diphosphate was determined. GK contains a region that is topologically identical to the adenosine triphosphate binding domains of hexokinase, the 70-kD heat shock cognate, and actin. IIIGlc binds far from the catalytic site of GK, indicating that long-range conformational changes mediate the inhibition of GK by IIIGlc. GK and IIIGlc are bound by hydrophobic and electrostatic interactions, with only one hydrogen bond involving an uncharged group. The phosphorylation site of IIIGlc, His90, is buried in a hydrophobic environment formed by the active site region of IIIGlc and a 3(10) helix of GK, suggesting that phosphorylation prevents IIIGlc binding to GK by directly disrupting protein-protein interactions.
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PMID:Structure of the regulatory complex of Escherichia coli IIIGlc with glycerol kinase. 843 Mar 15

Glycerol transport is commonly cited as the only example of facilitated diffusion across the Escherichia coli cytoplasmic membrane. Two proteins, the glycerol facilitator and glycerol kinase, are involved in the entry of external glycerol into cellular metabolism. The glycerol facilitator is thought to act as a carrier or to form a selective pore in the cytoplasmic membrane, whereas the kinase traps the glycerol inside the cell as sn-glycerol-3-phosphate. We found that the kinetics of glycerol uptake in a facilitator-minus strain are significantly different from the kinetics of glycerol uptake in the wild type. Free glycerol was not observed inside wild-type cells transporting glycerol, and diffusion of glycerol across the cytoplasmic membrane was not the rate-limiting step for phosphorylation in facilitator-minus mutants. Therefore, the kinetics of glycerol phosphorylation are different, depending on the presence or absence of the facilitator protein. We conclude that there is an interaction between the glycerol facilitator protein and glycerol kinase that stimulates kinase activity, analogous to the hexokinase- and glycerol kinase-porin interactions in mitochondria.
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PMID:Glycerol kinase of Escherichia coli is activated by interaction with the glycerol facilitator. 843 2


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