Oxidation of Unsaturated Fatty acids; The Most Important Points.

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Oxidation of Monounsaturated Fatty Acids(MUFA)

Unsaturated fatty acids such as Oleic acid are oxidized by same general pathway as saturated fatty acids.
But there are 2 special problems:

The double bonds of naturally occurring unsaturated fatty acids are in “cis“ configuration, whereas the Δ² (bond at position 2) of unsaturated acyl CoA intermediate in the oxidation of saturated fatty acids is in “trans“ position.
Moreover, the double bonds of most unsaturated fatty acids occur at such positions in the carbon chain that successive removal of 2C fragments from the carboxyl end yields a Δ³ unsaturated fatty acyl CoA rather than Δ2 fatty acyl CoA serving as normal intermediate in Fatty acid cycle.

This problem is resolved by an auxiliary enzyme Enoyl CoA isomerase which catalyzes a reversible shift of double bonds from “Δ3– cis“ to “Δ2– trans“ configuration, which is a normal substrate for next step/enzyme sequence i.e. Enoyl CoA hydratase.

Polyunsaturated fatty acids like Linoleic acid, require a second auxiliary enzyme to complete the oxidation as they have 2 or more “cis” double bonds.
When 3 successive acetyl CoA units are removed from Linoleoyl CoA, a “Δ3– cis“ double bond remains, as in case of Oleoyl CoA.
This is then transformed by Enoyl CoA isomerase to to “Δ2– trans“ isomer.
This undergoes the next usual reaction with removal of Acetyl CoA.
This leaves …

FOR COMPLETE LECTURE PLEASE VISIT THE COURSE PAGE IN BIOCHEMISTRY II SECTION. CLICK THE CURRICULUM TAB TO VIEW FULL LIST IN METABOLISM OF LIPIDS.