Fatty acid synthesis

Question 1

Location

Answer 1

liver
lactating mammary gland
adipose tissue
-cytosol

Question 2

Transport of Acetyl CoA from mitochondria

Answer 2

1. Acetyl CoA + OAA -> Citrate + CoASH
   - citrate synthase
   - citrate passes through membrane
2. Citrate +CoASH + ATP -> Acetyl CoA + OAA + ADP
   - citrate lyase

Question 3

Activation of Acetyl CoA to Malonyl CoA

Answer 3

Acetyl CoA + HCO3- + ATP -> Malonyl CoA +ADP +pi

• enzyme: ACETYL CoA CARBOXYLASE (biotin)
• FIRST COMMITTED STEP
• rate limiting step

Question 4

NADPH production

Answer 4

-pentose pathway
-Malate -> Pyruvate + CO2
malic enzyme

Question 5

Regulation of Acetyl CoA Carboxylase

Answer 5

activated by:
citrate
dephosphorylation
insulin-SREBP1

inhibited by:
palmitoyl-CoA
long chain fatty acyl CoA
phosphorylation of AMP activated protein kinase
glucagon

Question 6

Fatty acid synthase complex

Answer 6

• 3 domains
• reguires phosphopantetheine (prosthetic group, thirster bond, like a crane, carries substrate from one catalytic site to next)
• cysteine residue

Question 7

Priming of Acetyl CoA and Malonyl CoA

Answer 7

1. Acetyl-CoA + ACPSH -> Acety-ACP + CoASH
   - acetyl transacetylase
2. Malonyl-CoA + ACPSH -> Malonyl-ACP + CoASH
   - malonyl transacetylase

Question 8

1. Acetyl-ACP + Malonyl-ACP -> Acetoacetyl-ACP

Answer 8

• Acetyl-ACP + Malonyl ACP-> Acetoacetyl-ACP + CO2 + ACPSH
• condensation
• enzyme: BETA-KETOACYL-ACP SYNTHASE

Question 9

2. Acetoacetyl-ACP -> D-B-hydroxybutyryl-ACP

Answer 9

• reduction
• NADPH -> NADP+
• enzyme: BETA-KETOACYL ACP REDUCTASE

Question 10

3. D-B-hydroxybutyryl-ACP -> Crotonyl-ACP

Answer 10

• dehydration -H2O

- enzyme: BETA-HYDROXYACYL ACP DEHYDROGENASE

Question 11

4. Crotonyl-ACP -> Butyryl-ACP

Answer 11

• reduction
• NADPH -> NADP+
• enzyme: ENOYL ACP REDUCTASE
• after the reaction is repeated until 16C-palmitate

Question 12

5. 16C acyl ACP (Palmitate 16C)

Answer 12

• enzyme: THIOESTERASE
• cleave thioester linkage
• frees palmitate

Question 13

Elongation of saturated FAs

Answer 13

Palmitoyl CoA + malonyl CoA -> cond.->red.->dehyd->red. -> Stearyl-CoA
adding malonyl CoA every round
in sER

Question 14

Desaturation

Answer 14

• making unsaturated FAs
• in sER
• enzyme: FATTY ACYL CoA DESATURASE (O2, NADH, Cytb6)