FA Synthesis Flashcards
In humans, the ___ is the main site for FA synthesis
liver
note: other sites include: kidney, brain, lung, mammary gland, and adipose
The process of FA synthesis occurs in what part of the cell?
cytoplasm
FAs are synthesized from 2 carbon units (acetyl-CoA). ___ is the main source of the acetyl-CoA, with some contribution from ___
glucose; AAs
note: other cofactors/substrates include: NADPH, ATP, biotin, and HCO3-
The process of using acetyl CoA to produce FA in the cytosol requires two important enzymes. What are they?
- acetyl CoA carboxylase
2. FA synthase
When glucose is plentiful, glycolysis in the liver will produce “excess” ___ which enters mitochondria and produces ___-___ for the TCA cycle
pyruvate; acetyl-CoA
note: citrate, which is not further metabolized by the TCA can exit the mitochondria
In the cytosol, citrate is the substrate for ATP citrate lyase. What does this enzyme do? What does it require?
citrate is split back to oxaloacetate and acetyl-CoA
ATP is required
note: this enzyme is inducible
Cytosolic malate dehydrogenase reduces ___ to malate
OAA
What does the Malic enzyme do?
- converts malate to pyruvate
- produces NADPH which is necessary for FA synthesis
note: this enzyme is inducible
Acetyl-CoA carboxylase catalyzes the reaction producing ___-___ from acetyl-CoA
malonyl-CoA
Acetyl-CoA carboxylase requires ___ and is the rate-limiting enzyme of ___ ___
biotin; FA synthesis
Acetyl-CoA carboxylase is the regulated step of FA synthesis. It exists as either inactive ___ __ or as active ___.
proteomeric dimers; polymers
Acetyl-CoA carboxylase is stimulated by what? inhibited by what?
stimulated by citrate (feed forward)
inhibited by long-chain fatty acyl-CoA (feed back)
Acetyl-CoA carboxylase is also controlled by phosphorylation/dephosphorylation. True or false?
true
note: an AMP-dependent protein kinase phosphorylates the enzyme
Phosphorylation causes ___ of acetyl-CoA carboxylase?
inactivation
In regards to acetyl-CoA carboxylase, AMP would increase during times of ____
fasting
Glucagon stimulates the activity of the AMP-dependent kinase, which results in ___ of FA synthesis
inhibition
note: mechanism via cAMP-dependent protein kinase
A protein phosphatase dephosphorylates acetyl-CoA carboxylase. This causes ___ of the enzyme. This protein phosphatase is stimulated by ___
activation; insulin
Prolonged consumption of a diet containing excess calories results in increased synthesis of this enzyme
acetyl-CoA carboxylase
note: a low-calorie diet reduces synthesis of this diet
FA synthase is a multi-functional enzyme in eukaryotes. It is active as a ___. Each monomer contains ___ different enzymatic activities.
dimer; 7
FA synthase allows only one fatty acyl chain to be synthesized at a time. True or false?
false; two fatty acyl chains
FA synthase sequentially adds two-carbon units from ___-___ to a growing ___ ___ chain
malonyl-CoA; fatty acyl
The starting unit of FA synthase is ___-___ and the product is ____
acetyl-CoA; palmitate
- In the first round of the synthesis cycle, acetyl transacylase adds an acetyl group to the ___ of a cysteine residue of ketoacyl synthase domain of one monomer
SH
- Malonyl transacylase adds a malignly group to the SH of the ____-___ group of acyl carrier protein (ACP) domain of the other monomer
phospho-pantetheine