21 Lipids - Fatty acid synthesis

21 Lipids - Fatty acid synthesis - Lipids: Fatty Acid...

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Lipids: Fatty Acid Synthesis HNFE 3025 Fall 2009
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Synthesis of new fatty acids utilizing acetyl CoA derived from amino acid carbon skeletons and excess carbohydrate Primarily takes place in liver, adipose tissue and mammary gland. A positive energy balanced diet (especially one with high carbohydrate intake) will stimulate fatty acid synthesis from excess acetyl CoA An energy balanced diet containing 35% or more of fat will produce very little fatty acid synthesis de novo Fatty Acid Synthesis 2
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Takes place in the cytosol Malonyl CoA precursors must first be synthesized from acetyl CoA. Palmitate is the final product of synthesis This can be elongated or desaturated NADPH is the required reducing equivalent A multifunctional polypeptide enzyme system, fatty acid synthase (FAS), catalyzes the reactions de novo Fatty Acid Synthesis 3
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Acetyl CoA Product of carbohydrate or amino acid metabolism Malonyl CoA Produced from acetyl CoA by acetyl CoA carboxylase (ACC) 2 isoforms – ACC1 important for FA synthesis ACC2 important for the regulation of β -oxidation Precursors for FA Synthesis 4
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The majority of acetyl CoA is produced in the mitochondria Glucose, lactate, glycerol can be converted to pyruvate through glycolysis, which in turn is converted to acetyl CoA by PDH Part or all of glucogenic amino acids’ carbon skeletons are degrade to pyruvate or TCA cycle intermediates – all of which can be converted to acetyl CoA Ketogenic amino acids’ carbon skeletons are degraded to acetoacetate (which can be converted to 2 acetyl CoA) or acetyl CoA, directly. Sources of Acetyl CoA 5
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MCT Excess acetyl CoA is transferred to the cytosol for use in FA synthesis Citrate Shuttle 6 Malic enzyme Carbon skeletons of amino acids
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ACC1 and ACC2, carboxylase enzymes, contain a tightly bound biotin Bicarbonate is the source of carbon for the reaction Carboxyl group on malonyl CoA will provide the energy to drive the reactions of synthesis Formation of Malonyl CoA 7 Acetyl CoA Carboxylase
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FAS is a dimer of 2 identical subunits placed head-to-tail Each subunit is a single polypeptide chain in which there are a number of functional domains with enzyme activity.
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This note was uploaded on 03/23/2010 for the course HNFE 3025 taught by Professor Mwhulver during the Spring '10 term at Virginia Tech.

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21 Lipids - Fatty acid synthesis - Lipids: Fatty Acid...

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