Traufeller 2004 Biochim Biophys Acta
|Traufeller K, Gellerich FN, Zierz S (2004) Different sensitivities of CPT I and CPT II for inhibition by L-aminocarnitine in human skeletal muscle. Biochim Biophys Acta 1608:149-54.|
Abstract: L-Aminocarnitine (L-AC) has been shown to inhibit carnitine palmitoyltransferases (CPT) in rat muscle and in rat liver. However, there are no reports on interactions of L-AC with CPT II and CPT I of human muscle. Therefore, the aim of the present work was to characterize the inhibition of human muscle CPT I and CPT II by L-AC in muscle mitochondria, skinned fibers and muscle homogenates in comparison to the established action of malonyl-CoA. Both isoenzymes were inhibited by L-AC, but sensitivity was different (CPT I, Kd=3.8 mM L-AC; CPT II, Kd=21.3 μM L-AC). A mixed inhibition type in respect to carnitine was detected (Ki=3.5 μM L-AC). At 0.5 mM L-AC, CPT II was completely inhibited without affection of CPT I. In contrast, CPT I was completely inhibited by 0.4 mM malonyl-CoA (Kd=0.5 μM), whereas CPT II was nearly not affected by this inhibitor. Using these inhibitors in muscle homogenates, activities of CPT II and CPT I were detected to be 38±10% and 63±10% of total, respectively (n=21). In intact mitochondria and different fractions of muscle homogenates after selective solubilization of CPT II by Tween 20, the extent of specific CPT inhibition changed in relation to the accessible isoenzyme pattern. Palmitoyl-carnitine-dependent respiration in skinned fibers was inhibited by high concentrations of L-AC, indicating that the inhibitor can be transported via the acyl-carnitine transporter, too. The combined use of both inhibitors (L-AC and malonyl-CoA) allows the kinetic characterization of CPT I and CPT II in human muscle homogenates. In addition, it has been shown that L-AC can be used for the study of metabolic consequences of CPT II deficiency on function of intact mitochondria.
• Keywords: CPT, Human muscle mitochondria, Image -aminocarnitine, Inhibition
Organism: Human, Rat Tissue;cell: Skeletal muscle, Liver Preparation: Permeabilized tissue