1. RR PKA Hormone-sensitive lipase TAG DAG MAG glycerol FFA Hormone-sensitive lipase P See Fig 16.7 Horton Fat mobilization in adipocytes Note: insulin inhibits TAG mobilization

2. Fatty acid oxidation 1.Activation 2.Transport into mitochondria  oxidation cycle Acyl CoA synthetase (thiokinase) acylcarnitine transferase/acylcarnitine translocase acyl CoA dehydrogenase enoyl CoA hydratase L-3-hydroxy CoA dehydrogenase Thiolase

3. Acyl CoA synthetase R-COO- + CoA-SH + ATP R-C- S-CoA + AMP + PPi O Note: 4 different enzymes specific for FA of differing chain length. location: outer membrane of mitochondria, ER membranes

4. Transport of fatty acyl CoA into mitochondria Carnitine Fatty AcylCoA + carnitine acylcarnitine + CoA translocase Fatty AcylCoA + carnitine acylcarnitine + CoA Mito matrix Carnitine acyltransferase I Carnitine acyltransferase II Malonyl CoA

6. Net yield of ATP C 16 FA + CoA + ATP C 16 acyl CoA + AMP + PP1 C 16 acyl CoA + 7 NAD + 7 FAD 8 AcCoA + 7 NADH + 7 FADH 2 8 AcCoA 24 NADH + 8 FADH 2 + 8 GTP + 16 CO 2 31 NADH 77.5 ATP 15 FADH2 22.5 ATP 8 GTP 8 ATP 108 ATP - 2 ATP Net = 106 ATP

7.  -oxidation of unsaturated fatty acids Enoyl-CoA isomerase: converts diene to single double bond 2,4 dieonyl-CoA reductase: converts cis to trans double bond

8.  -oxidation of unsaturated fatty acids H 3 CCCCCCCCCCCCCC 6 8 10 1212 1414 1616 1818 C 4 C CO-S-CoA C 2 e.g. Linoleic acid: C 18 cis,cis-  9,12 3 rounds of  -oxidation 3 Ac-CoA Enoyl-CoA isomerase    H 3 CCCCCCCCCCC 8 10 1212 1414 1616 1818 CO-S-CoA C 12 cis,cis-  3,6   C 12 trans,cis-  2,6 H 3 CCCCCCCCCCC 2 4 6 8 10 1212 CO-S-CoA H 3 CCCCCCCCC C 10 cis-  4 24 6 8 1212 1round of  -oxidation Ac-CoA

9. H 3 CCCCCCCCC CO-S-CoA C 10 cis-  4 24 6 8 1212 H 3 CCCCCCCCC CO-S-CoA C 10 trans,cis-  2  4 24 6 8 1212 H 3 CCCCCCCCC CO-S-CoA C 10 trans-  3 24 6 8 1212 Acyl-CoA dehydrogenase 2,4 dieonyl-CoA reductase NADP H 3 CCCCCCCCC CO-S-CoA 24 6 8 1212 C 10 cis-  2 Enoyl-CoA isomerase continued  -oxidation

10.  -oxidation of odd numbered fatty acids Requires: Propionyl CoA carboxylase (biotin) - adds CO 2 methyl malony CoA racemase - converts D isomer of methyl malonyl CoA to L isomer methyl malonyl CoA mutase (adenosylcobalamin) - rearranges MMCoA to yield succinyl CoA

11. Oxidation of odd-numbered fatty acids CH 3 -CH 2 -C-S-CoA O - OOC-CH C-S-CoA O CH 3 O - OOC-CH C-S-CoA CH 3 C-S-CoA - OOC-CH 2 O CH 2 Proprionyl CoA D-methylmalonyl CoA L-methylmalonyl CoA succinyl CoA CO2CO2 Biotin, ATP adenosylcobalamin racemase mutase

12. Cobalamin B 12 adenosylcobalamin R = 5’-deoxyadenosinyl - intramolecular rearrangements methylcobalamin R = CH 3 - transfer of methyl groups See fig 7.24 Horton

13. Fatty acid biosynthesis Where: cytoplasm liver, fat cells When: good energy charge, insulin Process: 1.Transfer of AcCoA from mito to cyto 2.Acetyl CoA carboxylase 3.Fatty acid synthase

14. 1.Transfer of AcCoA from mito to cyto Citrate lyase Citrate + ATP + + CoA OAA + AcCoA + ADP + Pi mito cyto Pyruvate malate citrate AcCoA OAA AcCoA OAA Pyruvate citrate H+H+ Antiport with pyr or Pi Citrate lyase NADH NADPH

15. Question: Incubation of tissue using the above pathway with only one of succinate-2,3- 14 C or succinate-1,4- 14 C will result in the production of radiolabeled fatty acid. Identify which substrate will yield 14 C-fatty acids.

16. Acetyl-CoA carboxylase 1 (ACC 1) AcCoA + CO 2 + ATP malonyl CoA + ADP + Pi biotin - OOC CH 2 C - SCoA O Regulation: Hormonal control - AMP kinase - inhibited by PKA mediated phosphorylation - enhanced by insulin Allosteric regulation - citrate activates phospho form - inhibited by palmitoyl CoA glucagon (liver) adrenalin (adipocytes) Nutritional status

17. Adrenalin Glucagon cAMP PKA ACC(active) ACC-PO 4 (inactive) TAG lipase (inactive) TAG lipase-PO 4 (active) Malonyl CoA ACT Regulation of FA metabolism by phosphorylation PP2A AMP- activated kinase Note: insulin activates ACC by stimulating the dephosphorylation reaction phosphatase FA synthesis activates inhibits

18. Steps in FA biosynthesis 1. Loading: transfer to ACP and ketoacyl-ACPsynthase CH 3 C - SCoA O + ACP-SH CH 3 C – SACP + CoASH O i. CH 3 C - ACP O + S-Synthase C – S-Synthase + ACP-SH ii. CH 3 O - OOC - CH 2 C - SCoA O iii. - OOC - CH2CH2 C – S-ACP O ACP-SH CoASH

19. 2. Condensation: - OOC - CH2CH2 C – S-ACP O C – S-SynthaseCH 3 O + CH2CH2 C – S-ACP CH2CH2 O C –CH 3 O CO2CO2 HS-Synthase

20. CH2CH2 C – S-ACP O C –CH 3 OH H 4. dehydration CHCHC – S-ACP O CCH 3 H H2O CH2CH2 C – S-ACP O C –CH 3 O 3. reduction NADPH NADP CH2CH2 C – S-ACP O CCH 3 H OH CHCHC – S-ACP O CCH 3 H 5. reduction CHCHC – S-ACP O CH 2 CH 3 NADPH NADP

21. CHCHC – S-ACP O CH 2 CH 3 CH2CH2 C – S-ACP O CH 2 CH 3 CH2CH2 C – S-synthase O CH 2 CH 3 ACP-SH Synthase-SH - OOC - CH2CH2 C-SACP O C O CH2CH2 CO2 + Synthase-SH Subsequent rounds of synthesis - transfer of growing FA to S-Synthase - addition of 2 carbon units from malonyl-S-ACP

22. Chain elongation introduction of double bonds linoleic and linolenic acids synthesis of arachidonic acid – an important precursor of several biologically active molecules