L-CARNITINE UPTAKE BY ESCHERICHIA-COLI

The uptake of L‐carnitine by Escherichia coli044 K 74 which is able to metabolize L‐carnitine to γ‐butyrobetaine under anaerobic conditions was studied. The uptake system of E. coli was induced in the presence of L‐carnitine or crotonobetaine. The optimum influx of L‐carnitine was found to take place at 37 °C in phosphate buffer, pH 7.5. On the basis of the temperature dependence of the uptake rate an activation energy of 53.5 kJ/mol was estimated. The transport of L‐carnitine was energy dependent. The kinetics of L‐carnitine entry followed the MICHAELIS‐MENTEN relationship yielding a Km value of 5.3 · 10‐4 M and a Vmax of 154 nmol/min · mg protein. The transport system showed considerable structural specifity for trimethylamine carboxylic molecules. The results suggest that E. coli possesses an inducible, active and carrier‐mediated uptake system for L‐carnitine. Copyright © 1990 Wiley‐VCH