Fatty acyl-CoA esters

[1] The activation reaction normally occurs in the endoplasmic reticulum or the outer mitochondrial membrane.

This is an adenosine triphosphate (ATP)-requiring reaction with fatty acyl-CoA synthase (CoASH), yielding adenosine monophosphate (AMP) and pyrophosphate (PPi):[2] R-COOH + CoASH + ATP

R-CO-SCoA + AMP + PPi Different enzymes are specific for fatty acids of different chain length.

[2] This shuttle mechanism is required only for longer chain fatty acids.

Once inside the mitochondrial matrix, the fatty acyl-CoA derivatives are degraded by a series of reactions that release acetyl-CoA and leads to the production of NADH and FADH2.