2: Fatty Acid Synthesis Flashcards
What is the major source of carbon for FA synthesis?
Dietary carbs
Organs where FAS occurs
Mostly liver + adipose, brain, kidneys, lactating mammary glands
Two ends of a fatty acid
Carboxyl end, methyl end
Three phases of fatty acid synthesis
- Cytosolic entry of acetyl CoA
- Generation of malonyl coA
- FA chain formation
What enzyme does malonyl coA inhibit?
Carnitine acyltransferase
Enzyme that adds 2C from malonyl coA to a growing fatty acyl chain in seven reactions to make palmitate
Fatty acid synthase (FAS)
Describe the FAS complex
Large, multi-enzyme complex with two identical dimers head-to-tail; with seven different enzymes + acyl carrier protein (ACP)
Four steps in a cycle of FAS
- Condensation
- Reduction
- Dehydration
- Reduction
What induces gene expression of acetyl coA carboxylase and FA Synthase?
Low fat / high carb diet
Citrate lyase: stimulated by what three things? Inhibited by what two things?
Stimulated by: phosphorylation, glucose, insulin
Inhibited by: PUFAs, leptin
Acetyl coA carboxylase: which form is active/inactive?
Polymeric form: active
Monomer/dimer: inactive
Three enzymes regulated in fatty acid synthesis?
- Citrate lyase
- Acetyl coA carboxylase
- FA synthase
Is acetyl CoA active or inactive when phosphorylated?
Dephosphorylated = active
Two things that stimulate acetyl CoA carboxylase
Citrate, insulin
Four things that inactivate acetyl coA carboxylase
LCFAs, epi, glucagon, AMP
Three things that stimulate FAS enzyme
Phosphorylated sugars, insulin, glucocorticoids
Three things that suppress FA Synthase
High fats, high PUFAs, starvation
Why is it important to make longer chain FAs?
The brain requires them
Five essential FAs + their number value things
- Linoleic acid (18:2 w6)
- Linolenic acid (18:3 w3)
- Arachidonic acid (20:4 w6)
- Eicosapentanoic acid (EPA) (20:5 w3)
- Docosahexanoic acid (DHA) (22:6 w3)
What does linoleic acid form?
Arachidonic acid
What does linolenic acid form?
Eicosapentanoic acid, docosahexanoic acid
Besides palmitate, what is formed by FAS?
CoA, NADP+
