Carnitine transports long-chain acy

Carnitine transports long-chain acyl groups from fatty acids into the mitochondrial
matrix, so that they can be broken down through β-oxidation to acetate to obtain
usable energy via the citric acid cycle. In some organisms such as fungi, the acetate
is used in the glyoxylate cycle for gluconeogenesis and formation of carbohydrates.
Fatty acids must be activated before binding to the carnitine molecule to form
acyl-carnitine. The free fatty acid in the cytosol is attached with a thioester bond to
coenzyme A (CoA). This reaction is catalyzed by the enzyme fatty acyl-CoA
synthetase and driven to completion by inorganic pyrophosphatase.

The acyl group on CoA can now be transferred to carnitine and the resulting acyl-
carnitine transported into the mitochondrial matrix. This occurs via a series of
similar steps:
1. Acyl-CoA is conjugated to carnitine by carnitine acyltransferase I
(palmitoyltransferase) located on the outer mitochondrial membrane
2. Acyl-carnitine is shuttled inside by a carnitine-acylcarnitine translocase
3. Acyl-carnitine is converted to acyl-CoA by carnitine acyltransferase II
(palmitoyltransferase) located on the inner mitochondrial membrane.
The liberated carnitine returns to the cytosol.