Biochemistry - Fatty Acid Synthesis Slides PDF

Biochemistry BIO-5002A Fatty Acid Synthesis Dr Maria Vardakou Biochemistry, 8th BIO-0.51 Edition [email protected] Berg, Tymoczko, k Gatto and Stryer Biochemistry BIO-5002A...

Biochemistry BIO-5002A Fatty Acid Synthesis Dr Maria Vardakou Biochemistry, 8th BIO-0.51 Edition [email protected] Berg, Tymoczko, k Gatto and Stryer Biochemistry BIO-5002A Cellular Fatty Acid Factories In today’s lecture… Enzymatic steps of Fatty Acid degradation and the three stages of the degradation process Which are the final products of Fatty Acid degradation When is Fatty Acid synthesis necessary (some examples) Which are the differences between Fatty Acid degradation and synthesis Which are the precursors in Fatty Acid synthesis What is ‘Fatty Acid Synthase’ and it’s components Fatty Acid synthesis and its links with cancer Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acids: Degradation and Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS Oxidation Reduction Hydration Dehydration Oxidation Reduction Cleavage Condensation Activated Activated Activated Activated Acyl Acetyl Acyl Malonyl Group Oxidative Group process Redcucing Group process Group  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acids and their Storage Molecules Non-Esterfied Fatty Acids (NEFA) Tri-Acyl Glycerol (TAG) Long CH chain with a terminal Uncharged esters of carboxylate group (COOH) fatty acids with Fuel molecules glycerol Stored as triacylglycerols Fuel molecules Building blocks of Stored in adipose phospholipids and glycolipids tissue (adipocytes) (in biological membranes) Biochemistry BIO-5002A Cellular Fatty Acid Factories Triacylglycerols (TAGs) TAGs are highly concentrated stores of energy (why?) Tri-Acyl Glycerol (TAG)  Biochemistry BIO-5002A Cellular Fatty Acid Factories Triacylglycerols (TAGs) TAGs are highly concentrated stores of energy (why?) Because they are Reduced and Anhydrous Complete oxidation of fatty acids yields ~ 9 kcal/g (oxidation of carbohydrates and proteins yields only 4 kcal/g) TAGs are nonpolar; they are stored in nearly anhydrous form (polar carbohydrates are highly hydrated) Tri-Acyl Glycerol (TAG) 1 g of nearly anhydrous fat stores 6.75 times more energy as 1 g of hydrated glycogen A typical 70 kg man has fuel reserves of 100,000 kcal in TAGs; 24,000 kcal in protein; 600 kcal in glycogen and 40 kcal in glucose 100,000 kcal stored in TAGs ~ 11 kg of his total body weight 100,000 kcal stored in glycogen ~ 75 kg! He would be ~ 64 kg heavier! Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Degradation Dietary lipids are digested by pancreatic lipases (and colipase) Usually in form of TAGs they must be degraded to fatty acids before they can be absorbed across the intestinal epithelium Final digestion products are carried in micelles to the intestinal epithelium where they are transported across the plasma membrane Stable lipoprotein transport particles Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Degradation The use of Fatty Acids as Fuel Requires 3-stages of Processing 1. Mobilization of lipids (TAGs are degraded, released from adipose tissue and transported to the energy-requiring tissues) 2. Once there the fatty acids must be activated and transported into mitochondria for further degradation 3. Fatty acids are oxidised to acetyl CoA which then enters the citric acid cycle Biochemistry BIO-5002A Cellular Note: BeforeFatty Acid Factories entering the Fatty Acid Degradation oxidation process fatty acids are linked to CoA (with the use of ATP, CoA and the help of acylCoA Oxidation synthetase) Hydration Oxidation Cleavage (Mitochondrial β- Oxidation)  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Degradation – Some Interesting Points β-oxidation pathway completely degrades saturated fatty acids (FAs) that have an even number of C atoms Unsaturated and odd-chain fatty acids require additional steps for degradation The oxidation of unsaturated FAs (containing double bonds) requires an isomerase and a reductase The final degradation products of FAs containing an odd number of C atoms are a propionyl CoA and an acetyl CoA (rather  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Degradation – Some Interesting Points The acetyl CoA formed from FAs oxidation only enters the citric acid cycle if carbohydrate is also present (Acetyl CoA combines with oxaloacetate which is normally formed from pyruvate) “fats burn in the flame of carbohydrates” (Rosenfeld, 1895)  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Degradation – Some Interesting Points The acetyl CoA formed from FAs oxidation only enters the citric acid cycle if carbohydrate is also present (Acetyl CoA combines with oxaloacetate which is normally formed from pyruvate) “fats burn in the flame of carbohydrates” (Rosenfeld, 1895) When carbohydrate in not sufficient or absent acetyl CoA from FAs is diverted into forming ketone bodies (remember starvation) Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis Our typical diet meets our physiological needs for fatsSo… and Is lipids… it necessary? If so… When? Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis Our typical diet meets our physiological needs for fats and lipids…so…Is it necessary? If so… when? Under certain physiological conditions ex. During embryonic development and during lactation in mammary glands Only certain tissues can synthesize fatty acids: liver and adipose tissue (inappropriate fatty acid synthesis contributes to liver failure) Acetyl CoA (end product of FA degradation) is the precursor for most fatty acids Fatty Acids are synthesized by a complex of enzymes; for simplicity this complex is called Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS Oxidation Reduction Hydration Dehydration Oxidation Reduction Cleavage Condensation Oxidative process Redcucing process Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Intermediates are linked to Intermediates are linked to SH groups of CoA SH groups of ACP Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Intermediates are linked to Intermediates are linked to SH groups of CoA SH groups of ACP Enzymes are not linked Enzymes are joined in a single polypeptide chain Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Intermediates are linked to Intermediates are linked to SH groups of CoA SH groups of ACP Enzymes are not linked Enzymes are joined in a single polypeptide chain Oxidants are NAD+ and FAD Reductant is NADPH Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Intermediates are linked to Intermediates are linked to SH groups of CoA SH groups of ACP Enzymes are not linked Enzymes are joined in a single polypeptide chain Oxidants are NAD+ and FAD Reductant is NADPH Isomeric form of the Isomeric form of the hydroxyacyl intermediate hydroxyacyl intermediate is is L D Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis FATTY ACID DEGRADATION mirrors FATTY ACID SYNTHESIS BUT Takes place in the Takes place in the cytoplasm mitochondria Intermediates are linked to Intermediates are linked to SH groups of CoA SH groups of ACP Enzymes are not linked Enzymes are joined in a single polypeptide chain Oxidants are NAD+ and FAD Reductant is NADPH Isomeric form of the Isomeric form of the hydroxyacyl intermediate hydroxyacyl intermediate is is L D Requires the participation of a 3-carbon intermediate  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis Acetyl CoA + ACP acetyl ACP + CoA Malonyl CoA + ACP malonylACP + CoA  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis Acetyl CoA + ACP acetyl ACP + CoA Malonyl CoA + ACP malonylACP + Acetyl ACP+ Malonyl ACP CoA acetoacetyl ACP + ACP + CO2 (2C) (3C) (4C) Condensation (1C) Reaction  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthesis Acetyl CoA + ACP acetyl ACP + CoA Malonyl CoA + ACP malonylACP + Acetyl ACP+ Malonyl ACP CoA acetoacetyl ACP + ACP + CO2 (2C) (3C) (4C) (1C) Palmiate (C16) serves as a precursor for a variety of Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase Fatty Acid synthase is a multifunctional enzyme complex with 7 active sites! Present catalytic activities in a single polypeptide chain  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase Fatty Acid synthase is a multifunctional enzyme complex with 7 active sites! EnoylReducta se Inactive KetoReduc domains tase Ψ: Pseudo Acyl Carrier DeHydratase hioEsterase Protein Ketosynthase Malonylacetyl Structure not Transferase yet fully resolved Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase Individual Proteins of the Fatty Acid Synthase Protein Ab b. Acyl Carrier AC Protein P β-Ketoacyl-ACP KS synthase Malonyl-CoA-ACP MA Transferase T β-Ketoacyl-ACP KR reductase β-Hydroxyacyl- DH ACP dehydratase Enoyl-ACP ER Reductase  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Note: This is figure 22.28 from Berg, Tymoczko, Gatto and Stryer Biochemistry. They describe the process as ‘7 steps’. You could argue that the steps are only 6 since at step 7 the process starts again… you Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps The cycle begins when MAT (not shown) attaches an acetyl unit to ACP Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps The cycle begins when MAT (not shown) attaches an acetyl unit to ACP Step 1: Acetyl group is delivered to KS; MAT attaches a malonyl unit to ACP  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 2: ACP visits KS again; KS condenses the acetyl and malonyl units to form a β-ketoacyl product (attached to ACP) Condensa tion  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 2: ACP visits KS again; KS condenses the acetyl and malonyl units to form a β-ketoacyl product (attached to ACP) Condensa tion Step 3: ACP delivers β-ketoacyl product to KR; KR reduces the keto group to an alcohol Reduction Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 4: The β-hydroxyl product visits the DH; DH introduces a double bond (+ loss of H2O) Dehydrati on H 2O Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 4: The β-hydroxyl product vistis the DH; DH introduces a double bond (+ loss of H2O) Dehydrati on H 2O Step 5: The enoyl product is delivered to the ER; ER reduces the double bond Reduction  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 6: ACP hands the reduced product to KS and gets recharged with malonyl CoA by MAT ACP delivers product to KS and gets recharged with a new malonylCoa by MAT  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 6: ACP hands the reduced product to KS and gets recharged with malonyl CoA by MAT ACP delivers product to KS and gets recharged with a new malonylCoa by MAT  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 6: ACP hands the reduced product to KS and gets recharged with malonyl CoA by MAT ACP delivers product to KS and gets recharged with a new malonylCoa by MAT  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps Step 6: ACP hands the reduced product to KS and gets recharged with malonyl CoA by MAT ACP delivers product to KS and gets recharged with a new malonylCoa by MAT Step 7: KS condenses the two molecules on ACP, which is now ready to begin another cycle Condensa tion Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps This process is repeated until the thioesterase (TE) releases the final C16 palmitic acid product Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Catalytic Steps  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Some Interesting Points Increased expression of FAS is a phenotype common to most human carcinomas (cancer cells need increased fatty acid synthesis) FAS expression is an indicator of poor prognosis in breast and prostate cancer Recent Interest in FAS and fatty acid metabolism for the diagnosis and treatment of cancer  Biochemistry BIO-5002A Cellular Fatty Acid Factories Fatty Acid Synthase – Some Interesting Points FA synthesis is maximal when CH and Energy are plentiful and when FA are scarce Acetyl CoA carboxylase plays an essential role in regulating FA synthesis and degradation (it catalyses the production of malonyl CoA) Acetyl CoA is regulated locally but also from a variety of hormones