| Range |
~7X10^6 ions/cell/sec
|
| Organism |
Human Homo sapiens |
| Reference |
Gasbjerg PK, Knauf PA, Brahm J. Kinetics of bicarbonate transport in human red blood cell membranes at body temperature. J Gen Physiol. 1996 Dec108(6):565-75. p.571 right column bottom paragraphPubMed ID8972394
|
| Primary Source |
Glibowicka, M., B. Winckler, N. Aranfbar, M. Schuster, H. Hanssum, H. Rfiterjans, and H. Passow. 1988. Temperature dependence of anion transport in the human red blood ceil. Biochim. Biophys. Acta. 946: 345-358.PubMed ID3207750
|
| Method |
"On the basis of studies of chloride transport mainly at 0°C, the "ping-pong model" for anion exchange was proposed (Gunn and Frohlich, 1979 Frohlich and Gunn, 1986). According to this model, a transport site in the protein, unloaded or loaded with an anion, may either face the internal or the external compartment." |
| Comments |
"When the Arrhenius plots for Cl-, Br-, and F- were
fitted to two intersecting regression lines, the "break"
in the lines occurred at different temperatures for Cl-
(15°C) and Br- and F- (23-25°C), but at the same "critical"
turnover number of ~4×10^9 ions/cell/sec
(Brahm, 1977 Wieth and Brahm, 1985). The fact that
the break occurs at different temperatures for different
anions indicates that the nonlinear temperature dependence
is not related to a phase transition in the
membrane, which would occur at the same temperature
regardless of the anion substrate. If two straight
lines are used to fit the Arrhenius plot for HCO3- transport
(Fig. 3), they intersect around 13°C. Thus, for
monovalent anions, the break temperature ranges from
13 to 25°C, supporting the concept that the nonlinear
temperature dependence of anion transport is not related
to a phase transition in the membrane. The turnover
number for HCO3- transport at 13°C is ~4×10^9
ions/cell/sec, similar to the critical turnover number
for Cl-, Br-, and F-. Ions such as iodide, salicylate, and thiocyanate, which never reach the critical turnover number, show a constant
apparent activation energy (Dalmark and Wieth, 1972). The divalent anion sulfate showed a decrease in
the apparent Arrhenius activation energy when temperature
is raised above 30°C (primary source),
but the critical turnover number for sulfate was only
~7X10^6 ions/cell/sec, 500-600 times lower than that
for chloride." |
| Entered by |
Uri M |
| ID |
110858 |