Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transport properties of brush border microvilli and basal-lateral plasma membranes isolated from rat kidney cortex were studied by a millipore filtration technique. Brush border microvilli but not basal-lateral plasma membranes contain sodium dependent stereospecific transport system for D-glucose, L-phenylalanine and inorganic phosphate as indicated by saturability, countertransport and inhibition by structurally related compounds. Reduction of equilbrium uptake by increasing medium osmolarity suggests transport into an osmotically reactive space rather than binding to the membranes. Electrogenecity of the sodium-sugar and sodium-amino-acid cotransport system was established by their dependence on artificially imposed diffusion potentials. Also a NA+/H+ antiport system can be demonstrated in microvilli vesicles by demonstrating counterflow of both ions under short circuit conditions. Basal-lateral plasma membranes contain sodium independent stereospecific transport systems for sugars and amino acids. These results demonstrate a marked functional polarity of the cell membranes in respect to sodium dependent and sodium independent transport systems. This polarity in conjunction with the asymmetrical distribution of sodium between the intra- and extracellular space seems to enable the proximal tubule epithelial cells to perform active transepithelial transport.
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PMID:Polarity of proximal tubular epithelial cells in relation to transepithelial transport. 1 64

alpha-L-Fucosidase has been purified 12 000 fold from human placenta. The enzyme is a glycoprotein containing, by weight: 0.9% galactose; 1.9% mannose, 1.9% N-acetylglucosamine and 1.9% N-acetylneuraminic acid. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate separated proteins with molecular weights ot 55 000, 51 400 and 25 000. Resolution of the two larger protein bands varied with the gel system and these proteins may differ only in carbohydrate content. Gel filtration of te purified enzyme failed to separate the three proteins. Treatments with the cross-linking reagent dimethyl suberimidate prior to electrophoresis, resulted in a diminution of the original protein bands and the formation of oligomers with molecular weights of 80 000, 100 000, 130 000, and 144 000. These results suggest that the heavy (55 000 and 51 400) and light (25 000) proteins are structurally associated. The molecular weight of the native enzyme, measured by gel filtration, was dependent on the pH of the eluting buffer. At pH 5.0 or 6.0 a catalytically active peak was observed, with a molecular weight of 305 000. At pH 7.5 this peak was completely absent and the enzyme eluted as an asymmetrical peak with an apparent molecular weight of about 60 000. The reduction in apparent molecular weight at pH 7.5 was reversible by dialysis of isolated fractions at pH 6.0. In agreement with these findings the sedimentation coefficient was 8.5 S at pH 5.0 but only 3.6 S at pH 7.5. The results can be accounted for by the existence of a pH-dependent equilibrium between aggregated and dissociated forms of the enzyme or by pH-depedent conformational changes.
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PMID:Purification and characterisation of alpha-L-fucosidase from human placenta. pH-dependent changes in molecular size. 3 24

1. The asymmetrical nature of sugar affinity for the hexose transfer system in human red cells has been demonstrated using purified 4,6-O-ethylidene-alpha-D-glucopyranose (ethylidene glucose) to inhibit the exchange of glucose, 3-O-methyl glucose and galactose. 2. The half-saturation concentration for ethylidene glucose inside the cell is estimated at ca. 110 mM whereas on the outside the value for exchange inhibition is ca 11mM. 3. The asymmetrics of affinities of two related non-transportable inhibitors 1,2-O-isopropylidene-D-glucofuranose and methyl-2,3-di-O-methyl-alpha-D-glucopyranoside have also been studied. 4. From experiments at varying concentrations and on theoretical grounds the half-saturation concentration for non-transportable inhibitors on the outside surface is shown to be over-estimated by measuring inhibition of exchange. In consequence the actual asymmetry of affinities may be greater than observed. 5. Experiments with ethylidene glucose also suggest that conformational changes redistributing components of the hexose transfer system between inward and outward facing modes may occur.
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PMID:Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non-transportable inhibitors. 67 17

In the present experiments, selective quenching by trinitrophenyl groups as well as steady-state fluorescence polarization and differential polarized phase fluorescence techniques, using three different lipid soluble fluorophores, were used to directly examine the fluidity of the exofacial and cytofacial leaflets of rat small intestinal brush-border membranes. These studies revealed that the fluidity of the exofacial hemileaflet was greater than the cytofacial hemileaflet. Differences in the distribution of phosphatidylcholine and phosphatidylethanolamine, as assessed by phospholipase A2 treatment and trinitrophenylation of aminophospholipids, were, at least partially, responsible for the asymmetrical fluidity of the hemileaflets. Moreover, in vitro addition of benzyl alcohol (final concn 25 mM) preferentially fluidized the exofacial leaflet and concomitantly decreased leucine aminopeptidase activity but did not affect the activities of maltase, sucrase, alkaline phosphatase, or gamma-glutamyltranspeptidase. In vivo addition of the membrane-mobility agent 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanate] (A2C) (final concn 7.5 microM) preferentially fluidized the cytofacial leaflet and increased Na(+)-gradient-dependent D-glucose transport but not Na(+)-gradient-dependent L-leucine transport.
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PMID:Characterization and modulation of rat small intestinal brush-border membrane transbilayer fluidity. 201 33

Ischemia plays an important role in the development of neuropathies associated with various disorders, such as peripheral vascular occlusive diseases, necrotizing vasculitides, diabetes mellitus and nerve compression or trauma. Although a multiple mononeuropathy or an asymmetrical polyneuropathy is the usual clinical presentation of ischemic neuropathy, some patients present with a neuropathy that is mainly distal and symmetrical. Pathologically, nerve ischemia results in focal or multifocal central fascicular or sector fiber degeneration. These ischemic lesions tend to begin at mid-upper arm or midthigh level, which is the watershed zone of poor perfusion, and become more diffuse distally. Nerve ischemia at the level of distal small fascicles often induces sub-perineurial crescent lesion rather than central fascicular fiber degeneration. Physiologically, reduced nerve blood flow with endoneurial hypoxia has been demonstrated in experimental diabetic and galactose neuropathies. Endoneurial ischemia/hypoxia in galactose neuropathy appears to be due to increased intercapillary distances and constriction of trans-perineurial vessels resulting from endoneurial edema. Although acute ischemic neuropathy has been well investigated, little is known about functional or structural responses of peripheral nerve to chronic ischemia.
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PMID:[Ischemic neuropathy]. 209 82

Two enzymatic activities that split diadenosine triphosphate have been reported in Escherichia coli: a specific Mg-dependent bis(5'-adenosyl) triphosphatase (EC 3.6.1.29) and the bis(5'-adenosyl) tetraphosphatase (EC 3.6.1.41). In addition to the activities of these two enzymes, a different enzyme activity that hydrolyzes dinucleoside polyphosphates is described. After purification and study of its molecular and kinetic properties, we concluded that it corresponded to the 5'-nucleotidase (EC 3.1.3.5) that has been described in E. coli. The enzyme was purified from sonic extracts and osmotic shock fluid. From sonic extracts, two isoforms were isolated by chromatography on ion-exchange Mono Q columns; they had a molecular mass of about 100 kilodaltons (kDa). From the osmotic shock fluid, a unique form of 52 kDa was recovered. Mild heating transformed the 100-kDa isoform to a 52-kDa form, with an increase in activity of about threefold. The existence of a 5'-nucleotidase inhibitor described previously, which associates with the enzyme and is not liberated in the osmotic shock fluid, may have been responsible for these results. The kinetic properties and substrate specificities of both forms (52 and 100 kDa) were almost identical. The enzyme, which is known to hydrolyze AMP and uridine-(5')-diphospho-(1)-alpha-D-glucose, but not adenosine-(5')-diphospho-(1)-alpha-D-glucose, was also able to split adenosine-(5')-diphospho-(5)-beta-D-ribose, ribose-5-phosphate, and dinucleoside polyphosphates [diadenosine 5',5'''-P1,P2-diphosphate,diadenosine 5',5'''-P1,P3-triphosphate, diadenosine 5',5'''-P1,P4-tetraphosphate, and bis(5'-guanosyl) triphosphate]. The effects of divalent cations and pH on the rate of the reaction with different substrates were studied.
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PMID:Hydrolysis of bis(5'-nucleosidyl) polyphosphates by Escherichia coli 5'-nucleotidase. 255 71

Lesions of one cerebral hemisphere are associated with decreased glucose metabolism, oxygen metabolism, and blood flow in the contralateral cerebellar hemisphere. We used positron emission tomography to look for a functional relationship in cerebral metabolism between the cerebral cortex and the contralateral cerebellum in normal human subjects. Twenty-four normal subjects were scanned with [18F]fluoro-2-deoxy-D-glucose while in a resting state. Asymmetry in local CMRglu (LCMRglu) in the frontal cortex was strongly correlated with asymmetry in LCMRglu in the opposite direction in the cerebellar hemispheres (r = -0.60, p less than 0.001). Widespread subregions of the frontal cortex were found to contribute to this relationship. Considering these results together with previous studies demonstrating that frontal lesions are associated with decreased metabolism in the contralateral cerebellum, we conclude that the frontal cortex exerts a strong modulating influence on metabolism in the contralateral cerebellum in normal subjects, and that this influence may be asymmetrical.
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PMID:A relationship between metabolism in frontal lobes and cerebellum in normal subjects studied with PET. 326 82

The transport function and orientation of the reconstituted human erythrocyte glucose transporter was studied with liposomes made with bovine brain lipid or Escherichia coli lipid. Reconstitution was achieved by a simple octyl glucoside dilution method. The reconstituted transporters with either lipid showed identical counterflow transport activity, the same response to various inhibitors, and characteristic cytochalasin B (CB) labeling. Functional location and purification of the glucose transporter was performed by using gel-permeation high-performance liquid chromatography with octyl glucoside-containing buffer. The reconstituted transport activity was associated only with band 4.5 protein (preactin) and not with band 3 protein. Both CB binding and transport function of the reconstituted transporters were resistant to trypsin but susceptible to chymotrypsin digestion. However, both trypsin and chymotrypsin treatment of unsealed ghosts completely eliminated the CB labeling and transport function of the glucose transporter. In our reconstitution system the glucose transporters maintained a normal asymmetrical (right-side-out) orientation and good transport function. A specific monoclonal antibody against the glucose transporter inhibited CB labeling of the transporters on unsealed ghosts. This was not found with the reconstituted system; however, after freeze-thawing there was a significant inhibition of CB binding by the antibody. These findings suggest that the CB-binding site of the reconstituted transporter is on the inner side of the proteoliposomes.
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PMID:Human erythrocyte glucose transporter: normal asymmetric orientation and function in liposomes. 351 73

Following symmetrical bilateral infusion of D-glucose into the basal ventromedial hypothalamus (BVMH), using Alzet minipumps (1 microliter/h of 10% D-glucose for 6 days), average daily food intake was reduced by 27% for the period of treatment. Symmetrical bilateral infusions into the posterior medial hypothalamus had a transitory effect on feeding, as did asymmetrical and unilateral infusions. Infusion of L-glucose into the BVMH did not yield a chronic reduction in food intake. Included in the infused solutions were tracer amounts of [14C]glucose, [14C]proline or [14C]leucine to permit radioautographic estimations of infusate dispersal in the brain and axonal transport patterns from the infusion sites. Infusions were generally well-restricted to 1-1.5 mm of the cannulae tips, and descending transport of amino acids was highest in substantia nigra and midline structures of the mesencephalon and pons including central gray, ventral tegmental area, raphe and ventral tegmental nuclei. These results provide evidence for an energy intake regulatory mechanism situated in the BVMH whose outputs may modulate activity in the substantia nigra and midline brain stem areas.
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PMID:D-glucose infusions into the basal ventromedial hypothalamus and feeding. 617 Dec 96

In the final stages of the terminal glycosylation of N-linked complex oligosaccharides, UDP-galactose: N-acetylglucosamine beta-1,4-galactosyltransferase (galactosyltransferase) transfers galactose (Gal) onto the N-acetylglucosamine (GlcNAc) residue of each branch of a biantennary oligosaccharide. Purified rat liver Golgi galactosyltransferase was used with GlcNAc beta 1,2-Man alpha 1,6-(GlcNAc beta 1,2-Man alpha 1,3-)-Man beta 1,4-GlcNAc beta 1,4-(Fuc alpha 1,6-)-GlcNAc-Asn in order to determine the sequence of addition of Gal residues to the biantennary oligosaccharide. The different galactosylated products were separated by concanavalin A affinity chromatography and high voltage paper electrophoresis in borate. It was found that Gal was transferred at a much faster rate to the GlcNAc beta 1,2-Man alpha 1,3-branch than to the GlcNAc beta 1,2-Man alpha 1,6-branch, i.e. k1 was at least 5 times larger than k2. Also, k3 was larger than k4, indicating that most of the digalactosylated product "GG" was formed by the sequential addition of Gal to the Man alpha 1,3-branch followed by addition to the Man alpha 1,6-branch. The preferential galactosylation of the GlcNAc beta 1,2-Man alpha 1,3-branch may explain the formation of the asymmetrical oligosaccharides found in bovine and human IgG.
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PMID:Branch specificity of purified rat liver Golgi UDP-galactose: N-acetylglucosamine beta-1,4-galactosyltransferase. Preferential transfer of of galactose on the GlcNAc beta 1,2-Man alpha 1,3-branch of a complex biantennary Asn-linked oligosaccharide. 642 77


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