Fatty Acid Synthesis

Question 1

Where does FA synthesis occur?

Answer 1

Cytosol of mainly the liver, but also in adipose, brain, kidneys, lactating mammary glands.

Question 2

Function of citrate lyase:

Answer 2

Citrate –> ACoA in cytosol

Question 3

Regulation of citrate lyase:

Answer 3

+ glucose, insulin

- PUFAs, leptin

Question 4

Acetyl CoA carboxylase

Answer 4

ACC. Catalyzes ACoA –> MCoA
Rate limiting enzyme
Biotin cofactor

Question 5

Malonyl CoA inhibits:

Answer 5

CPT 1 (aka carnitine acyltransferase), which acts in beta oxidation.

Question 6

FAS structure

Answer 6

Composed of 2 dimers (head to tail orientation).

7 unique enzyme activities and acyl carrier protein (ACP).

Question 7

Overall reaction for palmitate synthesis

Answer 7

1 ACoA + 7 MCoA + 14 NADPH + 14 H+ ——>

1 Palmitate +14 NADP+ + 8 CoA + 6 H2O

Question 8

Reactions catalyzed by FAS

Answer 8

Con, Red, Deh, Red

Question 9

Points of regulation in FA synthesis (3)

Answer 9

1. citrate lyase
2. ACC
3. FAS

Question 10

Regulation of citrase lyase

Answer 10

+ phosphorylation

Gene expression induced by glc/insulin, but counteracted by PUFAs and leptin.

Question 11

Regulation of ACC

Answer 11

RLS!
Inactive in dimer form (active polymer)
Allosterically reg by + citrate and - PUFAs
+ DEphosphorylation

Question 12

Regulation of FAS

Answer 12

Allosteric affect (presence of phosphorylated sugars) increases affect.
Other common sense regulators.

Question 13

Elongation of FAs past palmitate

Answer 13

Done in SER and mito.
Lengthened at 2Cs at a time.
SER uses MCoA
Mito uses ACoA

Question 14

Which enzyme catalyzes desaturation of FAs?

Answer 14

Acyl CoA desaturases, and use NADPH or NADH and O2.

FA w/ double bond beyond C9 and C10 cannot be synthesized in humans (ex: omega 3, omega 6)

Question 15

Regulation of desaturases

Answer 15

Induced by insulin

Supressed by dietary PUFAs