MECHANISM OF CARNITINE TRANSPORT CATALYZED BY CARNITINE CARRIER FROM RAT-BRAIN MITOCHONDRIA

The transport mechanism of reconstituted carnitine carrier purified fr om rat brain mitochondria was studied kinetically. Short and medium ch ain acyl carnitine derivatives had much higher affinity to the carniti ne carrier in comparison with long chain acyl carnitine derivatives, t herefore both homologous (carnitine/carnitine) and heterologous (carni tine/acetylcarnitine) antiports were analysed. A complete set of half- saturation constants was established for various substrate concentrati ons on both the external and the internal side of the membrane. Bisubs trate initial velocity analyses of the exchange reaction resulted in a kinetic pattern which is consistent with a sequential antiport mechan ism. This type of mechanism implies formation of a ternary complex of the carrier with one internal and one external substrate molecule befo re the transport reaction occurs.