ISSN:
1432-1424
Keywords:
l-glutamic uptake
;
Acidic amino acids
;
System X AG −
;
Red blood cells
;
Frog Rana esculenta
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Evidence is presented that the high levels of internal l-glutamic and l-aspartic acid in frog Rana esculenta red blood cells are due to the existence of a specific carrier for acidic amino acids of high affinity K m = 3 μm and low capacity (Vmax) 0.4 μmol l-Glu · Kg−1 dry cell mass · 10 min−1. It is Na+ dependent and the incorporation of l-glutamic acid can be inhibited by l and d-aspartate and l-cysteic acid, while d-glutamic does not inhibit. Moreover, this glutamic uptake shows a bell-shaped dependence on the external pH. All these properties show that this carrier belongs to the system X AG − family. Besides the incorporation through this system, l-glutamic acid is also taken up through the ASC system, although, under physiological conditions, this transport is far less important, since it has relatively low affinity K m 39 μm but high capacity (V max) 1.8 μmol l-Glu · Kg−1 dry cell mass · 10 min−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00232428
Permalink
