Question

Pristanal (see Problem 20-33) can be oxidized to pristanate. Can this compound be further degraded by β oxidation and, if so, what are the reaction products?

Short answer

Propionyl-CoA would be the primary product.

Step-by-step solution

Definition of β oxidation

The metabolic process by which activated fatty acids are broken down in a sequence of steps to form acetyl-CoA, which subsequently enters the citric acid cycle, is known as β oxidation.

Step 2: Oxidized form of pristanal-pristanate

The oxidised form of pristanal-pristanate is as follows:

Degradation of pristanate

In the liver, pristanate (the conjugate base of pristanic acid, which is transformed to pristanoyl-CoA) can be degraded to propionyl-CoA by β oxidation.The reactions that occur during the first cycle of $\beta$oxidation are listed below.

1.Acyl-CoA oxidase reaction:

$\text{Pristanoyl-COA+FAD}\to {\text{2,3-pristenoyl-COA+FADH}}_{\text{2}}$

2.2-enoyl-CoA hydratase reaction:

$\text{2,3-pristenoyl-COA}\to \text{3-hydroxyoristanoyl-CoA}$

3.3-hydroxyacyl-CoA dehydrogenase reaction:${\text{3-hydroxyoristanoyl-COA+NAD}}^{\text{+}}\to {\text{3-ketopristanoyl-COA+NADH+H}}^{\text{+}}$

4.3-ketoacyl-CoA thiolase reaction:

$\text{3-ketopristanoyl-CoA+CoASH}\to \text{4,8,12-trimethyltridecanoyl-COA+propionyl-CoA}$

Hence, propionyl-CoA would be the primary product.