Octanoyl dehydrogenase

Medium chain acyl-CoA dehydrogenase deficiency apparent Km and Vmax values for fibroblast acyl-CoA dehydrogenase towards octanoyl CoA in patient and control cell lines. 

For every step of the P oxidation sequence there is a small family of enzymes with differing chain length preferences.6 7 For example, in liver mitochondria one acyl-CoA dehydrogenase acts most rapidly on M-butyryl and other short-chain acyl-CoA a second prefers a substrate of medium chain length such as n-octanoyl-CoA a third prefers long-chain substrates such as pal-mitoyl-CoA and a fourth, substrates with 2-methyl branches. A fifth enzyme acts specifically on isovaleryl-CoA. Similar preferences exist for the other enzymes of the P oxidation pathway. In Escherichia coli... 

Recent studies with bovine heart mitochondrial matrix preparations indicate that one of the major products of this pathway is octanoyl-ACP and these newly synthesized octanoyl moieties can be translocated directly to the lipoylation site of the glycine cleavage apo-H protein (S. Smith, 2007). Octanoylated mitochondrial proteins are the substrates for the enzyme lipoic acid synthase, which inserts two sulfur atoms at the C6 and C8 positions of the octanoyl moiety. These results are consistent with the hypothesis that one of the major roles of the mitochondrial FAS pathway in all eukaryotes is to ensure that an adequate supply of lipoyl moieties is always available to service the glycine cleavage enzyme and the alpha-ketoacid dehydrogenases that are essential to mitochondrial function. 

The octanoyl CoA that is the end-product of peroxisomal oxidation leaves the peroxisomes and the octanoyl group is transferred through the inner mitochondrial membrane by medium-chain-length acylcarnitine transferase. In the mitochondria, it enters the regular p-oxidation pathway, beginning with medium-chain-length acyl CoA dehydrogenase (MCAD). 

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