Oxidation and biosynthesis of fatty acids Flashcards
Stages of Fatty Acid Oxidation
- Activation of fatty acids
- Transport of Fatty Acyl CoA into the matrix of ` mitochondria
- Degradation to two-carbon fragments
Location of activation of fatty acids
outer mitochondrial membrane
Location of degradation to two carbon fragments
mitochondrial matrix
Process of Activation of FA
- FA are converted to CoA thioesters
- PPi released is hydrolysed
- 2 phosphoanhydride bonds are consumed to activate one FA to a thioester
enzyme that catalyzes conversion of FA to CoA thioesters
acyl-CoA synthetase
enzyme that hydrolyses PPi
pyrophosphatase
Reaction involved in Step 1 of FA Oxidation
FA + ATP Acyl adenylate + PPi
Acyl adenylate + HS—CoA Acyl CoA + AMP
Difference of Acyl CoA and Acetyl CoA
Acetyl CoA: R = methyl
Acyl CoA: R= Carbon chain of any length; two carbons shorter than Acetyl CoA
shuttling system used to transport FA into the mitochondria
carnitine shuttle system
Process of Transporting FA into mitochondria
- Fatty acyl CoA is first converted to acylcarnitine
- Acylcarnitine enters mitochondria (matrix side)
- acyl group is transferred back to CoA
enzyme that converts Fatty acyl CoA to acylcarnitine
carnitine acyltransferase I
carnitine acyltransferase I is bound to-
outer mitochondrial membrane
Acylcarnitine enters the mitochondria via-
translocase
enzyme that transfers acyl group back to CoA
carnitine acyltransferase II
B-carbon atom (C3) is oxidized
B-oxidation pathway
Number of atoms degraded in B-oxidation pathway at a time
2
Reactions in B-oxidation pathway
Oxidation
Hydration
Oxidation
Cleavage
Reaction in 1st Oxidation
Acyl CoA trans-Enoyl CoA
enzyme in 1st oxidation
acyl CoA dehydrogenase
coenzyme and oxidizing agent in 1st oxidation
FAD
Reaction in Hydration
trans- Enoyl CoA ——-> L-3-Hydroxyacyl CoA
enzyme in Hyration
enoyl CoA hydratase
alcohol formed in Hydration
L-3-Hydroxyacyl CoA
Reaction in 2nd Oxidation
L-3-Hydroxyacyl CoA ——-> 3-Ketoacyl CoA
enzyme in 2nd Oxidation
3-hydroxyacyl CoA dehydrogenase
coenzyme in 2nd Oxidation
NAD+
ketone formed in 2nd oxidation
3-Ketoacyl CoA
Reaction in Cleavage
3-Ketoacyl CoA ——–> Acyl CoA + Acetyl CoA
Coenzyme and Cofactors in Cleavage
HS-CoA
Enzyme in Cleavage
B-ketothiolase
- shortened by two C atoms
- undergoes another cycle of oxidation
Acyl CoA
will enter other cycles
Acetyl CoA
The formula for number of cycles
n/2 - 1
Each round generates one molecule each of:
FADH2
NADH
Acetyl CoA
Fatty Acyl CoA
Fate of NADH and FADH2 after B-oxidation
used in ETC
Fate of acetyl CoA after B-oxidation
enters TCA
Fate of acyl CoA after B-oxidation
undergoes the next cycle of oxidation
occurrence of Odd Chain fatty acids
bacteria
microorganisms
Final Cleaving product of B-Oxidation of Odd Chain FA
propionyl CoA rather than acetyl CoA
3 enzymes that convert propionyl CoA to succinyl CoA
propionyl CoA carboxylase
methylmalonyl-CoA racemase
cobalamin (Vit B12)
Type of reaction in first step of conversion of Propionyl CoA to succinyl CoA
Carboxylation
Hydrolysis of ATP
reaction in first step of conversion of Propionyl CoA to succinyl CoA
Propionyl CoA ———-> D-Methylmalonyl CoA
Enzyme in first step
propionyl CoA carboxylase
Coenzyme in first step
Cofactor in first step
biotin, ATP
HCO3
Type of reaction in second step of conversion of Propionyl CoA to succinyl CoA
Racemization
reaction in second step of conversion of Propionyl CoA to succinyl CoA
D-Methylmalonyl CoA L-Methylmalonyl CoA