TY - JOUR
T1 - Zero-trans and equilibrium-exchange efflux and infinite-trans uptake of galactose by human erythrocytes
AU - Ginsburg, Hagai
AU - Ram, Dalia
PY - 1975/3/25
Y1 - 1975/3/25
N2 - 1. 1. The zero-trans and equilibrium exchange efflux and the infinite-trans uptake of galactose in human erythrocytes were measured as a function of galactose concentration at 20%. 2. 2. The zero-trans procedure with cells loaded with 285 mM galactose revealed a low affinity site for galactose transport at the inner face of the membrane having a maximal velocity of 255±96 mmol/1 isotonic cell water and Km = 240±57 the V/K ratio being 1.01±0.04 min-1. 3. 3. The equilibrium-exchange procedure yielded a maximal velocity of 432±44 mmol/cell unit per min and K = 138±57, the V/K ratio being 3.19±0.52 min-1. 4. 4. The infinte-trans uptake revealed a high affinity site at the outer face of the membrane having a maximal velocity of 239±11 mmol/cell unit per min, and K = 21±2 mM. 5. 5. These results combined with previous findings (Ginsburg, H. and Stein, W. D. (1975) Biochim. Biophys. Acta 000,000-000) force us to reject the following models for sugar transport in human erythrocytes: a single asymmetric carrier; two symmetric carriers in parallel, the original form of the internal transfer model.
AB - 1. 1. The zero-trans and equilibrium exchange efflux and the infinite-trans uptake of galactose in human erythrocytes were measured as a function of galactose concentration at 20%. 2. 2. The zero-trans procedure with cells loaded with 285 mM galactose revealed a low affinity site for galactose transport at the inner face of the membrane having a maximal velocity of 255±96 mmol/1 isotonic cell water and Km = 240±57 the V/K ratio being 1.01±0.04 min-1. 3. 3. The equilibrium-exchange procedure yielded a maximal velocity of 432±44 mmol/cell unit per min and K = 138±57, the V/K ratio being 3.19±0.52 min-1. 4. 4. The infinte-trans uptake revealed a high affinity site at the outer face of the membrane having a maximal velocity of 239±11 mmol/cell unit per min, and K = 21±2 mM. 5. 5. These results combined with previous findings (Ginsburg, H. and Stein, W. D. (1975) Biochim. Biophys. Acta 000,000-000) force us to reject the following models for sugar transport in human erythrocytes: a single asymmetric carrier; two symmetric carriers in parallel, the original form of the internal transfer model.
UR - http://www.scopus.com/inward/record.url?scp=0016670470&partnerID=8YFLogxK
U2 - 10.1016/0005-2736(75)90278-3
DO - 10.1016/0005-2736(75)90278-3
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C2 - 1125239
AN - SCOPUS:0016670470
SN - 0005-2736
VL - 382
SP - 369
EP - 376
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 3
ER -