Interaction of sugar acetals with the human erythrocyte glucose transport system

Novak, Roger A.; LeFevre, Paul G.

doi:10.1007/bf01870193

Cited by 12 publications

(4 citation statements)

References 10 publications

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“…In isopropylidene glucose the dioxan ring structure involves the oxygens on carbon atoms 1 and 2 of the glucose molecule. Novak & LeFevre (1974) NON-TRANSPORTABLE INHIBITORS it to be among the class of non-transportable inhibitors and we have examined its inhibition when equilibrated inside cells which were suspended in a medium free of inhibitor as well as its inhibition when on the outside only. Fig.…”

Section: Inhibition Of Galactose and 3-0-methyl Glucose Exchangementioning

confidence: 99%

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Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non‐transportable inhibitors.

Baker¹,

Basketter²,

Widdas³

1978

The Journal of Physiology

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SUMMARY1. The asymmetrical nature of sugar affinity for the hexose transfer system in human red cells has been demonstrated using purified 4,6-O-ethylidene-oz-D-glucopyranose (ethylidene glucose) to inhibit the exchange of glucose, 3-0-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 11 mM.3. The asymmetries of affinities of two related non-transportable inhibitors 1,2-0-isopropylidene-D-glucofuranose and methyl-2,3-di-0-methyl-a-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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Section: Inhibition Of Galactose and 3-0-methyl Glucose Exchangementioning

confidence: 99%

“…Benzylidene glucose which was used in a few experiments was prepared as described by Novak & LeFevre (1974).…”

Section: Introductionmentioning

confidence: 99%

Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non‐transportable inhibitors.

Baker¹,

Basketter²,

Widdas³

1978

The Journal of Physiology

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“…Other, larger, analogs are not transported, for example the 6-O-propyl, 6-O-pentyl, and 6-O-benzyl derivatives of galactose (Barnett et al, 1975), as well as 4-azido-4-deoxy-D-galactose, 4-(2'-diazo-3',3',3'-trifluoropropionyl)-Dglucose , and 4,6-O-ethylidene-D-glucose (Baker & Widdas, 1973;Baker, Basketter & Widdas, 1978). In general, sugars with two or more hydroxyl groups cross-linked by isopropylidene substituents are not transported (Novak & LeFevre, 1974), and the same is true of still larger molecules such as maltose (Lacko & Burger, 1962) and bis-mannosyl compounds .…”

Section: Glucose Transportmentioning

confidence: 97%

“…The smaller ones tend to have a lower affinity than glucose, while some of the larger ones have a higher affinity. For example phenyl-fl-D-glucose (Barnett et al, 1975), 4,6-0-benzilidene-D-glucose (Novak & LeFevre, 1974) and bis-mannosyl compounds bearing a phenyl substituent (Midgley, Parker & Holman, 1985) are bound about 10 times more strongly than glucose. Such observations on the glucose carrier parallel those on the choline carrier, and both agree with expectation.…”

Section: Glucose Transportmentioning

confidence: 99%

Expression of substrate specificity in facilitated transport systems

Krupka

1990

J. Membrain Biol.

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In facilitated transport systems the carrier reorientation step is shown to be largely independent of the forces of interaction between the substrate and the carrier site, whereas in coupled systems (obligatory exchange or cotransport) reorientation proceeds at the expense of the binding force developed in the transition state. In consequence, the expression of substrate specificity is expected to differ in the two systems. In the facilitated transport of analogs no larger than the normal substrate, the affinity but not the maximum rate of transport can vary widely; with larger analogs, both the affinity and rate can vary if steric constraints are more severe in the translocation step than in binding. In coupled transport, by contrast, the translocation step can be highly sensitive to the structure of the substrate, and binding much less sensitive. The theory agrees with published observations on facilitated systems for choline and glucose in erythrocytes, as well as on Na(+)-coupled systems for the same substrates in other cells. The following mechanism, which could account for the behavior, is proposed. In facilitated systems, the transport site fits the substrate closely and retains its shape as the carrier undergoes reorientation. In coupled systems, the site is initially looser, but during carrier reorientation it contracts around the substrate. In both systems, the carrier encloses the substrate during the translocation step, though for a different reason: in coupled but not in facilitated systems the binding force enormously increases in the enclosed state, through a chelation effect. In both systems, steric interference with enclosure retards the translocation of bulky substrate analogs.

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75, 77Br- and 123I-analogues of d-glucose as potential tracers for glucose utilisation in heart and brain

et al. 1983

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A number of D-glucose analogues labelled with either the positron emitter 75Br (T 1/2 = 1.6 h) or the single photon emitter 123I (T 1/2 = 13.3 h) were studied as potential tracers for glucose utilisation in heart and brain. Of these, 3-deoxy-3-bromo-D-glucose, 3-deoxy-3-iodo-D-glucose, methyl 2-deoxy-2-bromo-beta-D-glucoside and methyl 2-deoxy-2-iodo-beta-D-glucoside showed little uptake of radioactivity into brain and an unfavourable ratio of heart-to-blood and heart-to-lung concentrations. In contrast, methyl 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-beta-D-glucoside (MTIG) and methyl 3,4,6-tri-O-acetyl-2-deoxy-2-bromo-beta-D-glucoside (MTBG) showed promising brain uptake (160% MBC for MTBG) with a good brain-to-blood concentration ratio of 0.8. MTBG is not metabolically altered in the brain. Thus, this compound may be a promising tracer for measuring glucose transport if it proves to be a substrate for the hexose carrier at the blood-brain-barrier.

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Interaction of sugar acetals with the human erythrocyte glucose transport system

Cited by 12 publications

References 10 publications

Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non‐transportable inhibitors.

Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non‐transportable inhibitors.

Expression of substrate specificity in facilitated transport systems

75, 77Br- and 123I-analogues of d-glucose as potential tracers for glucose utilisation in heart and brain

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