Lipid Metabolism Lecture 8 PDF

Dr. Ardina Grüber Nanyang Technological University School of Biological Sciences Division of Structural Biology and Biochemistry Singapore 637551 email: [email protected]  Energy expenditure during exercise...

Dr. Ardina Grüber Nanyang Technological University School of Biological Sciences Division of Structural Biology and Biochemistry Singapore 637551 email: [email protected]  Energy expenditure during exercise energysos is in - glycogen - fat http://highered.mheducation.com/sites/0072507470/student_view0/ch apter25/animation__energy_sources_for_prolonged_exercise.html  cas of Mathews, van Holde, Ahern: Biochemistry 3rd edition  thermal insulator fat florage ~ of lipids cells A generati & storage of energy -storage of energy - format of biological rembranes - intracellular signaling no. of mitot no. of mito It lipid + assumed toKave invoked in similar funch as brown adipocytes thermogenesis format : of heat Scanning electron micrograph of an adipose cell Garett & Grisham: Biochemistry 4th edition  Stored metabolic fuel in a 70-kg person esterificati Advantages for storing energy in the form of fatty acids: 1. The carbon in fatty acids is almost completely reduced compared to the carbon in sugars or amino acids. Therefore, oxidation of fatty acids will yield more energy in form of ATP than any other form of carbon. 1-Palmitoyl-2,3-dioleoyl-glycerol 2. Fatty acids are not generally as hydrated as monosaccharides are, and thus they can pack more closely in storage tissues. non-polar & tend interact fatty acids are to in additi , is do & pack closely in elo Voet, Voet: BIOCHEMISTRY 3rd edition Garett & Grisham: Biochemistry 4th edition  intake dietary Primary sources of fats released from food has to be emulsified TAGs Diet ~ De novo biosynthesis in the liver Storage depots in adipocytes or adipose cells. Because of their insolubility, fats are usually emulsified with bile salts or complexed with proteins as lipoproteins © 2016 Pearson Education, Ltd.  epinephrine glucagon , , etc. ~ Lunde Stress) (fasting) differ under diff could activate Synthesis of TAG and its deposition in 2nd adipose cells is unlimited + - messenger Mobilization of stored fat (lipolysis) is hormonally controlled via cAMP Mediated by epinephrine during stress phosphorylat situations and by glucagon during catalysing hydrolysis of fasting FA Other hormones regulate the process substrate under different conditions (parathyroid of DAG cleares another FA hormone etc.) ~ lipase substrate & Garett & Grisham: Biochemistry 4th edition  Alkaline pancreatic juice secreted into the duodenum raises the pH of the digestive cleare from mixture, allowing hydrolysis of the c, /d4 triacylglycerols by pancreatic lipase and by cleare FA of end of nonspecific esterases. they i triacylglycerol g from C e cleaneremaining. ,. for from here & ↳ These processes depend upon the presence of L bile salts. These agents act as detergents to emulsify the triglycerols and facilitate the hydrolytic activity of the lipases and esterases. The fatty acids pass into the epithelial cells, giving mixture o diff type of triacylglyperol where they are condensed with glycerol to form new triacylglycerols, which aggregate with lipoproteins to form particles called chylomicrons. & can be transported through lymph duct & bloodstream Garett & Grisham: Biochemistry 4th edition  Bile salts emulsify TAGs in the intestine Conjugation site rigidStructure of 4 fused rings cores Chydrophobic bile acids& bile salts are notI same amphipathic & © 2016 Pearson Education, Ltd. allowing for hydrolysis Bile acids are derivative of cholesterol Synthesized in the hepatocytes Cholesterol is converted into the bile acid cholic and chenodeoxycholoic acid a ~ organic. a. compound These bile acids are conjugated to glycine or taurine to yield anions called bile salts & site interacts w conjugati either to give bile salts © 2016 Pearson Education, Ltd.  Generalized plasma lipoprotein structure The spherical particle, part of which is shown, has a hydrophobic inner core (yellow) composed of cholesterol esters and triacylglycerols surrounded by a hydrophilic surface formed by the polar head groups of phospholipids and free cholesterol. a proteins useful for molecules © 2016 Pearson Education, Ltd. transporting non-polar  Classification of lipoproteins biggest lipop veryo a ipop ©Function 2016 Pearson Education, Delivery of Delivery of Delivery of Delivery of Picking up Ltd. dietary dietary and dietary and cholesterol excess fatty acids other other cholesterol from fatty acids fatty acids cells for delivery = IDL back to the liver they differ in size , appearance & content & functa  Fate of chylomicrons ~ presentinena interact wHDL important for interacts i C20), chain to medium/short 34 it is transported to mito for to long-chain fatty acids (C12 to C20), there are 2 types of B-oxidat ? medium-chain fatty acids (C6 to C12), and to) in mito directly one in mitochondria & another in peroxisores short-chain fatty acids (C4). or less 1. Saturated fatty acids 2. Unsaturated fatty acids 3. Fatty acids with odd numbered carbon chain COT, carnitine octanoyltransferase; CAT, carnitine acetyltransferase; CAC, carnitine acylcarnitine carrier; CPTI, carnitine palmitoyltransferase I; CPTII, carnitine palmityltransferase II  2nd Step 14 step of p to) ~ - Palmitoyl-CoA + 7 CoA-SH + 7 FAD + 7 NAD + + 7 H2O 8 Acetyl-CoA + 7 FADH2 + 7 NADH + 7 H+ activated & 329 undergo 7 cycles &f B [0) Step in order to create 8 acetyl-CoA Reaction ATP Yield Plo ratio for Activation of palmitate to palmitoyl-CoA -2 TCA cycle generates ATP NADH 2 5 Oxidation of 8 acetyl-CoA 10 8 x 10 = 80 : · one Oxidation of 7 FADH2 7 x 1.5= 10.5 FADH : 1 5. Oxidation of 7 NADH 7 x 2.5= 17.5 Net: Palmitate → CO2 + H2O 106 Mathews, van Holde, Appling, Anthony-Cahill: BIOCHEMISTRY 4rd edition  Energy yield for one cycle of β-oxidation of palmitic acid > e-transported - to ETC for oxidative phosphorylat to) 17 ATP to) for create acetyl cost http://www.wiley.com/college/pratt/0471393878/student/exercises/chapter_14.html  Energy yield for the complete β-oxidation of palmitic acid here i ploratio used is : NADH : 3 FADH2 : 2 1. & 12 molecules of ATP generated by Test cycle 2. (17 x 7) So e calculate of ATP 3. yield depends on p/o ratio used 4. 5. 6. 7. http://www.wiley.com/college/pratt/0471393878/student/exercises/chapter_14.html  usedto stances oxidise ~ s generated Very-long-chain fatty acids begin β- oxidation in the peroxisomes. diff 203 steps same me ~ entry than in e This process is almost identical to β- Mitochondria oxidation in the mitochondria, with one key difference. Instead of reducing ubiquinone in the first step, the peroxisomes produce hydrogen peroxide. & Hr2 does not contribute to ATP format ω-oxidation is an alternative pathway in some animal species. 15ATP minor catabolic pathway for medium chain fatty acid become more important when β-oxidation is defect. as I molecules of ATP contributed by QU2 in oxidative phosphorylate are here missing http://www.wiley.com/college/pratt/0471393878/student/exercises/chapter_14.html  Oxidation of fatty acids with odd numbered carbon chains The final product of b-oxidation of odd-carbon fatty acids ~ source of carboxyl is bicarbonate is the three-carbon propionyl-CoA. carries carboxyl grp from one The pathway involves an initial carboxylation at the a- carbon of propionly-CoA to produces D-methylmalonyl- ~ Molecule to another CoA. The reaction is catalyzed by a biotin-dependent enzyme, propionyl-CoA carboxylase. X The mechanism involves ATP-driven carboxylation of biotin, followed by nucleophilic attack by the a-carbanion subfrate of propionyl-CoA in a stereospecific manner. L cost & responsible for changing H) grp from 2x to C , - I I L & Conversion of propionyl-CoA to succinyl-CoA is carried out by a trio of enzymes. Succinyl-CoA can enter the TCA cycle. & & contribute to ATP yield Leninger Principles of BIOCHEMISTRY 4rd edition (MADH & FADH2 in oxidative phosphorylate)  more kinks ! double bood introduces kink , so kinky ! A shape of FA Voet, Voet: BIOCHEMISTRY 3rd edition 13 12 18 9 undergoes normal B [02 UB ~ anal func" is to Unsaturated fatty acids are also catabolized by b-oxidation, but 1. transform. 2 trans also = shifts = betw two additional mitochondrial enzymes: B Y B & x f & to B betw – an isomerase and => making e E , it a substrate allowing / cycle for – a novel reductase f B 50] are required to handle the cis double bonds. As shown for linoleic acid, b-oxidation proceeds three cycles, introduce trans and enoyl-CoA isomerase converts the cis-D3 double bond to = betw x & B 2 atom - trans-D2 double bond to permit one more round of b-oxidation. What results is a cis-D4 enoyl-CoA, which is oxidized to the trans-D2, cis-D4 species by acyl-CoA dehydrogenase. createsore trans = befor B & & c atom from 2 ~ double bonds The subsequent action of 2,4-dienoyl-CoA reductase yields the [H)] trans-D3 product, which is converted by enoyl-CoA ismerase to u B the trans-D2 form. X B Garett & Grisham: Biochemistry 4th edition  condensati of acctyl-cost The process in which acetyl-CoA is converted to three important metabolites: acetone, rxtoanta acetoacetate and b-hydroxybutyrate is known as ketogenesis, and the metabolites are known as ketone bodies. Ketone bodies are synthesized primarily in the liver (mitochondrial matrix) but are important sources of fuel release and energy for many tissues, including brain, heart, and molecule f acetyl-cort skeletal muscle. under condit like fasting & Narrath [AD") , Ketone bodies are easily transportable forms of fatty acids T when E converts & ~ 15 before - hydroxybutyrate aretoacetate to that move through the circulatory system without the need body formed for complex formation with serum albumin and other fatty acid-binding proteins. actoacetate & B-hydroxybutyrate are in equ , equ is dependent on [MAB + ] & INADHS when [MADH] is high Garett & Grisham: Biochemistry 4th edition  Acetoacetyl-CoA b-Hydroxy-b-methyl- glytaryl CoA ~ trof Cort from succinyl-cof Acetone Acetoacetate D-b-Hydroxybutyrate to acctoacetate The Lynen cycle describes the formation of acetoacetate from two molecules of Acetyl-CoA. The cycle results in the formation of 2 HSCoA molecules and 1 acetoacetate. ~ one molecule of Coff Reconversion of ketone bodies to acetyl-CoA in the mitochondria of many tissues (other than liver) provides significant metabolic energy. Karlson, P.: Biochemistry for medicine and science 13th edition Voet, Voet: BIOCHEMISTRY 3rd edition Acetyl-CoA is a key intermediate between fat and carbohydrate metabolism Arrows identify major routes of formation or utilization of acetyl-CoA. Citrate serves as a carrier to transport acetyl units from the mitochondrion to the cytosol for fatty acid synthesis. Note that acetyl-CoA is readily converted into fatty acids, but acetyl- CoA cannot undergo net conversion to carbohydrate.  A comparison of fatty acid ↳C 33 Voet, Voet: BIOCHEMISTRY 3rd edition  catabolism of a. s Amino (not sufficient acids TCA : well needs to transport acetyl-CoA in mito to cytosol (from a radate of FA & decarboxylat citrate out of pyruvate by PDH in mito) phosphate/malate in supply reduct Cantiporter) equivalents citrate malate CO2 pyruvate Shuttle Cantiporter) ~ e-donor for FA synthesis NAD+ NAD+ Glycolysis NADH + H Pyruvate NADH + H NADH used in dehydrogenase Glucose © 2016 Pearson Education, Ltd.  ATP-dependent - ~ bicarbonate : source of carboxyl gup acetyl-CoA carboxylase The carboxylation of acetyl-CoA to form Malonyl-CoA malonyl-CoA is essentially irreversible and is the committed step in the synthesis of fatty acids. activate of bicarbonate of bicarbonate) The reaction is catalyzed by acetyl-CoA Phosphorylate cleared carboxylase (ACC), which contains a biotin prosthetic group and is regulated by phosphorylation, allosteric modification and Nu attack induction/repression if its synthesis. carboxyl gup attached to Citrate allosterically activates acetyl CoA biotin carboxylase by causing the individual enzyme molecules to polymerize. & leadia theybecome active Palmitoyl-CoA, the final product of fatty acid X biosynthesis, inhibits acetyl CoA carboxylase. transport of (feedback inhibity) carboxy gup X Malony- CA Garett & Grisham: Biochemistry 4th edition  The fatty acid synthase complex has seven different active sites In E. coli and some plants, the seven active sites for fatty acid synthesis (six enzymes and ACP) reside in seven separate polypeptides. In these complexes, each enzyme is positioned with its active site near that of the preceding and succeeding enzymes of the sequence. The flexible pantetheine arm of ACP can reach all the active sites, and it carries the growing fatty acyl chain from one site to the next; intermediates are not released from the enzyme complex until it has formed the finished product. have these all these polypeptides some organisms organized in a huge complex single peptides that internet other organisms have = elo © 2016 Pearson Education, Ltd.  The b-ketoacyl-ACP synthase catalyzes the decarboxylative condensation of the acyl group with malonyl-ACP to produce an acetoacetyl-ACP. tisf molecule from ACP to KS There are two crucial differences between fatty acid biosynthesis and fatty acid oxidation: decarboxylat? 1. the alcohol formed in biosynthesis of malonyl pantetheine - 6A arm has the D-configuration rather than the L-form; 2. the reducing coenzyme is NADPH, whereas NAD+ and FAD are the oxidants in the catabolic pathway. introduct = betw C- & CB reduct of BX before gup to alcohol - orfum s Lehninger: Principles of Biochemistry, 4th edition in mito 22 unit donor 1 molecule & GA Shorter chains are easily made if the chain is released released before reaching 16 carbons in length. and fatty sunthrennget Longer chains are made through special elongation reactions, which occur both in the mitochondria and at the surface of the endoplasmatic reticulum (ER). [H) Elongation in the ER involves the successive condensations of malonyl-CoA with acyl-CoA and the NADPH-associated reduction. The mitochondrial reactions involve addition (and subsequent reduction) of acetyl units. hydrat These reactions are essentially a reversal of fatty acid oxidation, with the exception that NADPH is utilized in the saturation of the double bond, instead of FADH2. CH] Voet, Voet: BIOCHEMISTRY 3rd edition new molecule : 22 atom longer than carta material  ↑ 18 double bord introduced befor Ca & Go total 4e-transferred, donate e- 2 from NABH , & 2 from Gl Stearyl - which is dehydrogenated Both pro-and eukaryotes are capable of introducing a single cis double bound in a newly synthesized fatty acid. Bacteria and eukaryotes carry it out in an O2-independent and O2-dependent pathway, respectively. In eukaryotes this reaction is catalyzed by a desaturase. NADH, O2 and the two proteins cytochrome b5 reductase and cytochrome b5 are required. All these proteins are associated with the ER membrane. Cytochrome b5 reductase transfers a pair of e- from NADH through FAD to cytochrome b5. Oxidation of reduced cytochrome b5 is coupled to reduction of nonheme Fe3+ to Fe2+ in the desaturase. Thus Fe3+ accepts a pair of e- from cytochrome b5 and creates a cis double bond in the fatty acid. O2 is the terminal e- acceptor in the fatty acyl desaturation cycle. Note that two H2O molecule are made, which means that four e- are transferred overall. Two of these come through the reaction sequence from NADH, and two come from the fatty acyl substrate that is being dehydrogenated. Mathews, van Holde, Ahern: Biochemistry 3rd edition Voet, Voet: BIOCHEMISTRY 3rd edition  ~ controla Control of fatty acid ① synthesis T insulin glucose uptake by introducts of glucose transporter in plasma memb Insulin promotes glucose uptake, promotes dephosphorylation (activation) of pyruvate dehydrogenase, citrate lyase, acetyl-CoA carboxylase (ACC) ② activate PDH phosphatase AMP-activated protein kinase and protein kinase A promote phosphorylation of acetyl-CoA carboxylase (inhibition) activteem Citrate (activation) and long-chain fatty acids (inhibition) are also allosteric modulators of ③ activat ACC citrate Iyase Malonyl CoA inhibits carnitine acyl transferase of the outer mitochondrial membrane inhibiting ① influences the ACC the transport of fatty acyl CoA into mitochondrial matrix. © 2016 Pearson Education, Ltd.