Abstract
1. Experiments are reported on the entry, exit and exchange fluxes of L-leucine in human erythrocytes in the temperature range 0-37° C. The kinetics of entry and exit become quite different at low temperatures, indicating an asymmetry in the transport mechanism.
2. The data is analysed in terms of a simple carrier mechanism. This shows that carrier re-orientation is rate determining at all temperatures studied, and suggests, although does not prove, that the origin of the asymmetry of the carrier may be an unequal equilibrium distribution of the carriers between inward and outward orientations.
3. The activation energy increases sharply on going to low temperatures. This increase is the sum of two components. One arises from differences between the activation energies for inward and outward carrier re-orientations, and the other from changes, with temperature, in the activation energies of the individual carrier re-orientation steps.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- DAWSON A. C., WIDDAS W. F. VARIATIONS WITH TEMPERATURE AND PH OF THE PARAMETERS OF GLUCOSE TRANSFER ACROSS THE ERYTHROCYTE MEMBRANE IN THE FOETAL GUINEA-PIG. J Physiol. 1964 Jul;172:107–122. doi: 10.1113/jphysiol.1964.sp007406. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hoare D. G. The transport of L-leucine in human erythrocytes: a new kinetic analysis. J Physiol. 1972 Mar;221(2):311–329. doi: 10.1113/jphysiol.1972.sp009753. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kotyk A. Mobility of the free and of the loaded monosaccharide carrier in Saccharomyces cerevisiae. Biochim Biophys Acta. 1967 Feb 1;135(1):112–119. doi: 10.1016/0005-2736(67)90013-2. [DOI] [PubMed] [Google Scholar]
- SEN A. K., WIDDAS W. F. Determination of the temperature and pH dependence of glucose transfer across the human erythrocyte membrane measured by glucose exit. J Physiol. 1962 Mar;160:392–403. doi: 10.1113/jphysiol.1962.sp006854. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WINTER C. G., CHRISTENSEN H. N. MIGRATION OF AMINO ACIDS ACROSS THE MEMBRANE OF THE HUMAN ERYTHROCYTE. J Biol Chem. 1964 Mar;239:872–878. [PubMed] [Google Scholar]