EFFECT OF PALMITOYLCARNITINE ON MITOCHONDRIAL ACTIVITIES

Mitochondria from pea (Pisum sativum L. cotyledons and potato (Solanum tuberosum L.) tubers exhibited a palmitoyl carnitine-dependent, KCN-s ensitive stimulation of the oxygen uptake measured in the presence of 0.2 mmol . 1(-1) malate (sparker malate), provided a certain concentra tion range of palmitoylcarnitine was observed. Above this concentratio n range, which was dependent on the bovine serum albumin (BSA) concent ration of the reaction mixture, the mitochondrial oxygen uptake was in hibited by palmitoylcarnitine. Palmitoylcarnitine (racemate) and palmi toyl-L-carnitine were equally effective in stimulating/inhibiting mito chondrial oxygen uptake in the presence of sparker malate. The mitocho ndrial membrane potential generated in the presence of sparker malate was partially dissipated by palmitoyl-L-carnitine concentrations stimu lating the mitochondrial oxygen uptake. The formation of acid-soluble radioactivity in reaction mixtures provided with [1-C-14]palmitoyl-L-c arnitine was considerably lower than that expected minimally if the pa lmitoyl-L-carnitine-stimulated oxygen uptake resulted from palmitoyl-L -carnitine oxidation sparked by malate. Palmitoylcarnitine concentrati ons resulting in stimulation of the mitochondrial oxygen uptake in the presence of sparker malate also led to a stimulation of succinate-cyt ochrome c reductase activity, as well as to an increase in the measura ble activities of mitochondrial matrix enzymes, indicating loss of bot h mitochondrial integrity and mitochondrial enzyme latency in the pres ence of palmitoylcarnitine. Correspondingly, malate-dependent NADH for mation was stimulated by palmitoylcarnitine. Neither NAD reduction nor oxygen uptake were observed when the mitochondria were provided with palmitoylcarnitine only. The oxygen uptake due to glycine oxidation by mitochondria from green sunflower (Helianthus annuus L.) cotyledons w as affected by palmitoylcarnitine in a similar manner to the oxygen up take of pea cotyledon and potato tuber mitochondria in the presence of sparker malate. The results lead to the conclusion that the palmitoyl carnitine-dependent stimulation of mitochondrial oxygen uptake observe d in the presence of sparker malate results substantially from an enha nced malate oxidation due to the detergent effect of palmitoylcarnitin e on the mitochondrial membranes, rather than from palmitoylcarnitine beta-oxidation.