Open AccessAmino Acid Transport in Plasma‐Membrane Vesicles from Rat Liver
Author(s) -
SIPS Herman J.,
AMELSVOORT Johan M. M.,
DAM Karel
Publication year - 1980
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1980.tb04492.x
Subject(s) - symporter , alanine , chemistry , sodium , vesicle , membrane , membrane transport , amino acid , biophysics , biochemistry , transporter , biology , organic chemistry , gene
Plasma‐membrane vesicles, isolated from rat liver, catalyze active transport of L‐alanine. The transient accumulation of L‐alanine requires the presence of a Na + concentration gradient (outside> inside). The alanine‐Na + symport is an electrogenic process, since it is stimulated under conditions that allow compensatory ion movements: both co‐transported anions as well as counter‐transported cations influence the rate of alanine‐Na + symport. However, no uptake is observed in the presence of a membrane potential, when no Na + concentration gradient is present. Sodium‐gradient‐stimulated alanine uptake is dependent on temperature and pH, stereospecific, and is affected by the presence of other amino acids. The activity of the L‐alanine transport system is influenced both by the Na + and by the l ‐alanine concentration. In the presence of 100 mM Na + , an apparent K m for alanine of 2 mM is observed; lowering the Na + concentration results in an increase in the apparent K m , and a decrease in the apparent V. The apparent K m for Na + is 34 mM in the presence of 0.2 mM l ‐alanine. Increasing the L‐alanine concentration also results in a lower apparent K m for Na + and a higher V.