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Fatty Acid Synthesis ((2) Activation of Acetyl CoA and Formation of NADPH,…
Fatty Acid Synthesis
Three Stages of Fatty Acid Synthesis
(1) Transfer of Acetyl CoA out of the Mitochondria into the Cytoplasm
– Citrate is transported into the cytoplasm and cleaved into oxaloacetate and acetyl CoA
(2) Activation of Acetyl CoA
– forms malonyl CoA
(3) Repetitive Addition and Reduction of two carbon units–
synthesizes a C16 Fatty Acid on an acyl carrier protein
(1) Transfer of Acetyl CoA out of the Mitochondria into the Cytoplasm
Citrate is synthesized in the mitochondria and then transported into the cytoplasm
ATP-citrate lyase cleaves Citrate and generates Acetyl CoA
(2) Activation of Acetyl CoA and Formation of NADPH
NADPH is reducing power for FA synthesis
ATP-citrate lyase can oxidize oxaloacetate by the combined action of cytoplasmic malate dehydrogenase and malic enzyme– forms NADPH
Pentose Phosphate Pathway– forms NADPH
Acetyl CoA carboxylase synthesizes Malonyl CoA–
COMMITTED STEP
(3) Repetitive Addition and Reduction of two carbon units
ROUND 1
– Fatty Acid Synthase catalyzes the formation of fatty acids
Occurs on a acyl carrier protein (ACP)
Acetyl Transacylase and Malonyl Transacylase attach substratess to the ACP
Beta-Ketoacyl synthase catalyzes the condensation of acetyl ACP and malonyl ACP– forming acetoacetyl ACP
Next Three Steps: Reduction, Dehydration, Reduction– converts keto group at C-3 to a methylene group
Forms butyryl ACP
ROUND 2
– Butyryl ACP condensation with malonyl CoA– forms C6-beta-ketoacyl ACP
Reduction, Dehydration, Reduction
Continues until C16-acyl ACP is formed
Thioesterase cleaves C16-acyl ACP to yield palmitate