Open AccessAmino acid transport in membrane vesicles of Clostridium thermoautotrophicum
Author(s) -
Hugenholtz Jeroen,
Ljungdahl Lars G.
Publication year - 1990
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1990.tb04186.x
Subject(s) - glycine , alanine , serine , amino acid , chemistry , vesicle , kinetics , glycine cleavage system , membrane transport , substrate (aquarium) , biochemistry , membrane , biology , enzyme , ecology , physics , quantum mechanics
A proton motive force (Δp) generated by oxidation of CO in membrane vesicles of Clostridium thermoautotrophicum drove active transport of l ‐alanine, glycine and l ‐serine. The maximum rate ( V max ) for l ‐alanine transport was 12 × higher at 50°C than at 25°C. The apparent transport constant ( K t ) for l ‐alanine uptake was 30–40 μM and independent of the temperature. Glycine was a substrate for the l ‐alanine transport system as demonstrated by the competitive inhibition of l ‐alanine uptake by glycine ( K i = 6 μ M), by the kinetics of glycine uptake ( K t = 7 μ M) and by the inhibiton of glycine uptake by l ‐alanine. The uptake kinetics of glycine was biphasic. l ‐Serine inhibited competitively also l ‐alanine and glycine transport but it was taken up by a separate transport system. The rate of amino acid transport, but not the K t , was dependent on the value of the proton motive force.