A 22 kDa polyanion inhibits carnitine-dependent fatty acid oxidation in rat liver mitochondria

Area of Science:

• Mitochondrial biology
• Fatty acid metabolism

Background:

• The transport of activated fatty acids into mitochondria is essential for energy production.
• The precise mechanisms governing this transport across the mitochondrial outer membrane remain incompletely understood.

Purpose of the Study:

• To investigate the role of potential components involved in carnitine-dependent fatty acid oxidation across the mitochondrial outer membrane.

Main Methods:

• Utilized a 22 kDa polyanion as an inhibitor.
• Assessed the effects of the polyanion on ADP-stimulated oxidation of palmitoyl-CoA, palmitate plus CoA, palmitoylcarnitine plus malate, and glutamate.
• Examined mitochondrial hexokinase binding and carnitine palmitoyltransferase-1 activity.

Main Results:

• The polyanion significantly inhibited ADP-stimulated oxidation of palmitoyl-CoA and palmitate plus CoA, as well as hexokinase binding.
• Oxidation of palmitoylcarnitine plus malate and glutamate oxidation were largely unaffected.
• Mitochondrial carnitine palmitoyltransferase-1 activity remained uninhibited by the polyanion.

Conclusions:

• The findings indicate the involvement of an additional component, distinct from carnitine palmitoyltransferase-1, in the carnitine-dependent transport of activated fatty acids across the mitochondrial outer membrane.
• Porin is proposed as a potential candidate for this additional component.