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Glucose transport carrier activities in extensively washed human red cell ghosts

1971; Elsevier BV; Volume: 241; Issue: 2 Linguagem: Inglês

10.1016/0005-2736(71)90059-9

1879-2642

Chan Y. Jung, Linda Carlson, David A. Whaley,

Hemoglobin structure and function

Human red cell ghosts were prepared and extensively washed in the presence of divalent cations (Ca2+ and Mg2+) and their residual glucose transport carrier activities were studied. 99.18 % of the original cellular contents of hemoglobin were removed by the isolation procedures. The glucose carrier activities of such ghosts exhibited the following characteristics. (1) An extremely high permeability to d-glucose (2.0·10−5 cm/sec at 24°) and to 2-deoxy-d-glucose (2.9·10−5 cm/sec at 24°), compared with the permeability to d-mannitol (5.2·10−8 cm/sec at 24°). (2) Stereospecificity towards various sugars; relative rates of permeation by 2-deoxy-d-glucose, d-glucose, d-mannose and d-ribose were 1.5, 1.0, 0.35 and 0.020, respectively. (3) Saturability (for d-glucose at 24°, a Km of 19.5 mM and a Φmax of 6.4 μmoles·cm−3·sec−2). (4) Sensitivity to stilbestrol (competitive inhibition with a Ki of 4.69 μM at 24°) and to dinitrofluorobenzene (irreversible inhibition). (5) Transient uphill movements of d-glucose by the addition of a second sugar, 2-deoxy-d-glucose, a counter-transport phenomenon. (6) Relative insensitivity to change in pH, between 5.2 and 9.0. (7) High degree of temperature dependency with a negative Q10 for Km at low temperatures. (8) A relative resistivity to heat inactivation up to 65°. In conclusion, this work provides (1) the first evidence that such purified ghosts maintain fully functional glucose carrier activity and (2) a new detailed description of the nature of the temperature dependence and heat denaturation of this carrier system in ghosts.