Biochem Lecture 25- Fatty Acid Metabolism Part II

What four things do you get out of Beta oxidation of odd chain fatty acids?

NADH, FADH2, Propionyl-CoA (3 carbons), and Acetyl Co-A

What is the order of types of reactions (i.e. hydration, oxidation, etc.)

oxidation --> hydration --> oxidation --> thiolysis

What is the fate of the acetyl-CoA formed in the thiolysis reaction?

It enters the TCA cycle.

What happens to the propionyl-Co-A?

It is carboxylated?

What kind of enzyme is the propionnyl-CoA carboxylase? What does that mean it involves?

It is an ABC enzyme. It involves ATP, Biotin, and CO2.

What is the handiness that propionyl Co-A is converted to (L or D)? What enzyme does this?

It is converted to D-Methylmalonyl-CoA by the enzyme propionyl-CoA carboxylase.

Which enzyme turns the D-methylmalonyl-CoA to the L form?

Methylmalonyl-CoA Epimerase

Which rare cofactor is required by the methyl-malonyl-CoA Mutase to turn the L-methylmalonyl-CoA to succinyl-CoA?

Coenzyme B12

Where does the succinyl-CoA enter?

TCA cycle (duh)

Which 5 amino acids can be converted to Propionyl CoA and D-methylmalonyl-CoA?

Methionine, threonine, leucine, isoleucine, and valine.

How can a monounsaturated fatty acid be modified so it can undergo beta oxidation?

An isomerase reaction can take place to turn a cis double bond on the 3-4 Carbon into a trans double bond on the 2-3 Carbon (the alpha-beta carbons).

What is not able to be produced in beta oxidation of monounsaturated fatty acids (when the double bond is dealt with)?

FADH2

What does the dehydrogenase do to a polyunsaturated fatty acid?

It adds another double bond that is trans. Then the reductase can change the configuration.

Which reductive carrier is used in the reductase reaction in polyunsaturated fatty acids?

NADPH

Where are VLCFAs oxidized?

In peroxisomes

What all do peroxisomes do?

Beta Oxidation of VLCFAs, Plasmalogen synthesis, and alpha oxidation of phytanic acid.

What are VLCFAs initially shortened to? Where is that then transferred to?

MCFAs, which is then transferred to the mitochondria for further beta oxidation.

What is the acetyl-CoA produced in peroxisomes used for?

Biosynthesis

What does the brain use as its energy source is glucose levels are low (during starvation)?

Ketone bodies

What are the three types of ketone bodies?

Acetone, acetoacetate, beta-hydroxybutyrate

What is the rate limiting enzyme of ketogenesis? What product does this enzyme catalyze? Where in the cell does ketogenesis occur?

The rate limiting enzyme is HMG-CoA synthase, and it catalyzes the production of HMG-CoA. Ketogenesis occurs in the mitochondrial matrix.

What does ketogenesis regenerate?

CoA, which is required for B-oxidation of fatty acids.

Which ketone body is most common when there is a high concentration of NADH? In about what ratio is it found with the other ketone body?

Beta-Hydroxybutyrate, and it is found in a 3:1 ratio to acetoacetate.

In the process of starvation, which enzyme is upregulated in the brain?

Triophorase

What factors regulate ketogenesis?

Substrate availability (more fatty acids available leads to more ketogenesis), regulation of B-Oxidation, and the stimulation of HMG-CoA synthase.

How can you test for ketone bodies?

Urine analysis (rothera's test) and a blood test. However B-hydroxybutyric acid can't be detected in urine tests because there is not ketone functional group present.