Digesting Fatty Acids
In the adipocytes, the enzyme triacylglycerol lipase releases the fatty acids which are carried by albumin to tissues that need them such as the muscle.
In the muscle the fatty acids are activated by being bound to coenzyme A by the enzyme acyl CoA synthetase that catalyzes the following reaction:
Note that this reaction costs us two ATP equivalents and generates a pyrophosphate. The subsequent hydrolysis of the pyrophosphate renders the reaction irreversible.
At this point, the structure of the fatty acid makes a difference:
- Fatty acids with 9 carbons or fewer, they flow into the mitochondria.
- Fatty acids with 10 or more carbons are carried into the mitochondria on a molecule of carnitine
. - The enzyme carnitine acyltransferase I joins the fatty acid to carnitine:
- A translocase then transports the fatty acyl-carnitine across the mitochondrial membranes.
- The enzyme carnitine acytransferase II then transfers the fatty acid back to Coenzyme A:
