Question

The β-oxidation of odd-numbered FAs presents a small problem in that once most of the oxidation has occurred, the last component is propionyl-CoA rather than acetyl CoA. This has one more carbon and as such cannot be utilized any further. Outline the events that control the metabolism of this unit in their proper order:

1) Methylmalonyl-CoA epimerase converts S-methylmalonyl-CoA to R-methylmalonyl-CoA.

2) Methylmalonyl-CoA mutase demethylates R-methylmalonyl-CoA to succinyl-CoA.

3) Propionyl-CoA carboxylase catalyzes the addition of CO2 to propionyl-CoA.

4) The odd-carbon FA is metabolized to propionyl-CoA.

A) 4-3-1-2

B)3-1-4-2

C)4-1-3-2

D)2-1-3-4

Answer 1

4) The odd-carbon FA is metabolized to propionyl-CoA.

3) Propionyl-CoA carboxylase catalyzes the addition of CO2 to propionyl-CoA.

1) Methylmalonyl-CoA epimerase converts S-methylmalonyl-CoA to R-methylmalonyl-CoA.

2) Methylmalonyl-CoA mutase demethylates R-methylmalonyl-CoA to succinyl-CoA.

The correct order is A) 4-3-1-2