?

Biochemistry

Free Version

Upgrade subject to access all content

Moderate

Fatty Acid Oxidation: Polyunsaturated Fatty Acid

BIOCHM-B8QNIW

β-oxidation is used to metabolize saturated fatty acyl-CoA molecules to acetyl-CoA using the 4 enzyme-catalyzed reactions shown in the scheme below. Unsaturated fatty acyl-CoA molecules, on the other hand, cannot be completely metabolized using just these 4 steps.

NEUROtiker. "File:Beta-Oxidation1.svg." Beta-oxidation. Wikimedia Commons, 7 Jan. 2007. Web. 15 June 2016. https://commons.wikimedia.org/wiki/File:Beta-Oxidation1.svg.(Modified by M. Rumpho-Kennedy).

Consider the structure of the polyunsaturated fatty acid linoleic acid (${ C18:2\Delta }^{ 9,12 }$), shown in its fatty acyl-CoA form, below.

Created for Albert.io. Copyright 2016. All rights reserved.

Which of the following statements is NOT true concerning the oxidation of linoleoyl-CoA?

A

β-oxidation will initially proceed through 3 passes without the need for any additional enzymes and 3 acetyl-CoA will be generated.

B

After the original cis-${ \Delta }^{ 9 }$ bond is repositioned and converted to the trans configuration, β-oxidation can proceed directly to completion yielding a total of 9 acetyl-CoA.

C

After 3 passes through β-oxidation, linoleoyl-CoA is oxidized to a 12-C unsaturated fatty acyl-CoA intermediate with 2 cis double bonds at ${ \Delta }^{ 3,6 }$.

D

The β-oxidation enzyme enoyl-CoA hydratase cannot act on double bonds in the cis configuration.

E

Fatty acids with an even number of double bonds, such as seen in linoleic acid, require both an isomerase and a reductase to reposition and convert the cis double bonds to trans, in addition to the 4 enzymes of β-oxidation.