Nature of nonenzymatically bound hexose in hemoglobin, albumin, and crystallin

Kumar, Anuradha; Sharma, K. Krishna; Pattabiraman, T. N.

doi:10.1016/0006-2944(85)90068-7

Cited by 4 publications

(1 citation statement)

References 13 publications

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“…Evidence for a permeability barrier (Dx = 0.0005 s'1) to movements of sugars inside rat erythrocytes has been described previously , and nonuniform distributions of D-glucose inside human red cells have also been noted (Naftalin et al, 1985). Whether these findings result from associations of intracellular sugar with hemoglobin (Naftalin & Holman, 1977;Bolli et al, 1982;Gillery et al, 1982;Ink et al, 1982;Irzhakh, 1988;Krishnamoorthy et al, 1983;Kumar et al, 1985;Mortensen & Brahm, 1985; Mortensen & Christophersen, 1983;Shapiro et al, 1979;Widness et al, 1980) or from the presence of an unstirred glucose layer below the plasma membrane remains to be resolved.…”

Section: Discussionmentioning

confidence: 88%

Mechanisms for the facilitated diffusion of substrates across cell membranes

Carruthers

1991

Biochemistry

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Two classes of theoretical mechanisms for protein-mediated, passive, transmembrane substrate transport (facilitated diffusion) are compared. The simple carrier describes a carrier protein that exposes substrate influx and efflux sites alternately but never both sites simultaneously. Two-site models for substrate transport describe carrier proteins containing influx and efflux sites simultaneously. Velocity equations describing transport by these mechanisms are derived. These equations take the same general form, being characterized by five experimental constants. Simple carrier-mediated transport is restricted to hyperbolic kinetics under all conditions. Two-site carrier-mediated transport may deviate from hyperbolic kinetics only under equilibrium exchange conditions. When both simple- and two-site carriers display hyperbolic kinetics under equilibrium exchange conditions, these models are indistinguishable by using steady-state transport data alone. Seven sugar transport systems are analyzed. Five of these systems are consistent with both models for sugar transport. Uridine, leucine, and cAMP transport by human red cells are consistent with both simple- and two-site models for transport. Human erythrocyte sugar transport can be modeled by simple- and two-site carrier mechanisms, allowing for compartmentalization of intracellular sugars. In this instance, resolution of the intrinsic properties of the human red cell sugar carrier at 20 degrees C requires the use of submillisecond transport measurements.

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