How is fatty acyl CoA transported from the cytoplasm to the mitochondria for beta-oxidation?
Cytoplasmic fatty acyl CoA is converted to fatty acyl carnitine by carnitine acyl transferase (CAT I), an enzyme of the inner leaflet of the outer mitochondrial membrane. Fatty acyl carnitine is then trransported by an antiport in exchange for free carnitine to the inner surface of the inner mitochondrial membrane. There carnitine acyl transferase II (CAT II) reverses the process, producing fatty acyl CoA and carnitine. This shuttle mechanism is required only for longer chain fatty acids. Medium- and short chain fatty acids are carnitine-independent. They cross the mitochondrial membranes, and are activated in the mitochondrion.
