Mechanism of carnitine transport catalyzed by carnitine carrier from rat brain mitochondria

Abstract

The transport mechanism of reconstituted carnitine carrier purified from rat brain mitochondria was studied kinetically. Short and medium chain acyl carnitine derivatives had much higher affinity to the carnitine carrier in comparison with long chain acyl carnitine derivatives, therefore both homologous (carnitine/carnitine) and heterologous (carnitine/acetylcarnitine) antiports were analysed. A complete set of half-saturation constants was establiblished for various substrate concentrations on both the external and the internal side of the membrane. Bisubstrate initial velocity analyses of the exchange reaction resulted in a kinetic pattern which is consistent with a sequential anti port mechanism. This type of mechanism implies formation of a ternary complex of the carrier with one internal and one external substrate molecule before the transport reaction occurs.