Pre-steady-state uptake of D-glucose by the human erythrocyte is inconsistent with a circulating carrier mechanism.
Simulation shows that the four-state mobile carrier model for sugar transport in which the asymmetry arises from unequal rate constants of inward and outward translation of the free-carrier and carrier-sugar complex, does not fit with the observed data for pre-steady-state uptake recently obtained by A.G. Lowe and A.R. Walmsley [1987) Biochim. Biophys. Acta 903, 547-550). The main reason for this discrepancy is that pre-steady-state fluxes are determined mainly by the dissociation constants Ks of glucose and maltose for the external sites, rather than the Km (zero-transoi) of glucose and the Ki of maltose. The data are also inconsistent with other forms of asymmetric carrier but are fairly consistent with a symmetrical carrier with high-affinity sites for D-glucose or with a fixed site carrier model.
Naftalin
R J
RJ
Department of Physiology, King's College London, U.K.
D001692:Biological Transport; D001786:Blood Glucose / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008320:Maltose / Q000097:blood; D009004:Monosaccharide Transport Proteins / Q000097:blood*
D001786:Blood Glucose; D009004:Monosaccharide Transport Proteins; D008320:Maltose