Although enzymes of the pathway handle both short and long chain fatty acids, it is the long chain compounds that induce the enzymes of the pathway . Each turn of the cycle removes two carbon atoms until only two or three remain. When even-numbered fatty acids are broken down, a two-carbon compound remains, acetyl-CoA. When odd number fatty acids are broken down, a three-carbon residue results, propionylCoA. Unsaturated fatty acids, with cis double bonds located at odd-numbered carbon atoms, enter the main pathway of saturated fatty acid degradation by converting related metabolites of cis configuration and D stereoisomers, derived from breakdown of unsaturated fatty acids, to the trans- or L isomers of saturated fatty acid breakdown by an isomerase and an epimerase, respectively. When cis double bonds are located at even-numbered carbon atoms, such as linoleic acid (cis,cis(9,12)-octadecadienoic acid), after the fatty acid is degraded to the ten carbon stage an extra step is required to deal with the resulting compound, trans,δ(2)-cis,δ(4)decadienoyl-CoA. The enzyme 2,4-dienoyl-CoA reductase, converts this to trans,δ(2)decenoyl-CoA which enters the normal cycle at the point of the isomerase. The order of the reaction is as follows: a 2,3,4 saturated fatty acid is transformed into a 2,3,4 saturated fatty acyl CoA through a Long and short chain fatty acid CoA ligase. The 2,3,4 saturated fatty acyl CoA is then transformed into a trans 2 enoyl CoA. This enoyl can also be produced from a cis 3 enoyl CoA through a fatty acid oxidation protein complex. The trans 2 enoyl is transformed into a 3s 3 hydroxyacyl CoA through a 2,3 dehydroadipyl CoA hydratase. This same enzyme turns the product into a 3-oxoacyl-CoA. This is followed by the last step in the reaction when the oxoacyl-coa is turn into an acetyl coa+ a 2,3,4 saturated fatty acyl CoA through a 3-ketoacyl-CoA thiolase

Fatty Acid Oxidation (Myristate) References