Lipids 2

Aceteyl co A + ATP + HCO3- --> malonyl co A + ADP + Pi

Enzyme = acetyl co A carboxylase (biotin carboxylase and transcarboxylase)


Large negative change in G

Biotin.

Reacts with CO2 (HCO3-) to make a "charged" CO2 so it can transfer to acetyl co A

Cytosol

Mitochondria

Acetyl co A + OAA --> citrate

Citrate can translocate through the mitochondria membrane.

Cleave citrate --> OAA + acetyl co A in the cytosol.

Uses ATP to do this

To be converted to malate (via malate dehydrogenase, NADH --> NAD+)

Can be translocated into cytosol or converted to pyruvate via malit. This reaction removes CO2 via oxidative decarboxylation. Generates a NADPH that can feed into fatty acid synthesis

fatty acid synthase complex

Contains 7 enzyme activities and contains an acyl carrier protein (ACP)

B site contains pantothonic acid (reactive thiol) and adds malonyl co A via malonyl transferase activity

The C site contains a cystein (SH) and is part of the ACP portion of fatty acid synthase. Adds acetyl group of acetyl co A via acyl transferase activity. thioester bond

• 1. Condensation--acyl group of C site condenses with CH2 of malonyl residue, releases a CO2. = 4 Carbon = B-ketoacyl
• (beta ketoacyl synthase)

• 2. Reduction of C=0 to form a hydroxyl group
• B-ketoacyl reductase

• 3. Dehydration to eliminate water and form a C=C
• (dehydrogatase enzyme)

• 4. Reduction of C=C using NADPH to get a fully saturated 4 carbon butyryl group.
• (reductase enzyme)

5. Move B ketoacyl butyryl group from B site to the C site, allow another acetyl malonyl to bind to B site.

6. Repeat up to 15 times

7. Cleave off C site with thioesterase to release FFA

Add malonyl co A to the fatty acid chain using enzymes (not fatty acid synthase enzymes)

On they cytoplasmic side of the ER in most tissues for up to C18. Brain can go up to C24.

We can't introduce double bonds past carbon 10 in the ER, so we need to consume these fats from our diet.

mixed function oxidases in the ER

Activates = high levels of citrate (precursor for fatty acid synthesis)

Inhibits = palmityl CoA (product of fatty acid synthesis)

Glucagon and Epinephrine stimulate phosphorlation (and inactivation) of this enzyme

Fasting conditions (dont want to make fats--need to break them down)

Stimulates citrate lyase to convert more citrate to acetyl co A.

Stimulates PDH complex to increase production of acetyl co A.

Both these effects will increase the amount of fatty acid synthesis

ACP contains the B site which is made up of panthonic acid.

Adds another NADPH that can be used for anabolic processes in the cytosol.