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Review Session

Review Session . Saturday, 3 pm PH 104. Figure 25-17 Problems in the oxidation of unsaturated fatty acids and their solutions. Page 920. V. Figure 25-18 Conversion of propionyl-CoA to succinyl-CoA. Page 922. Figure 25-19 The propionyl-CoA carboxylase reaction. Page 922.

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Review Session

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  1. Review Session Saturday, 3 pm PH 104

  2. Figure 25-17Problems in the oxidation of unsaturated fatty acids and their solutions. Page 920

  3. V

  4. Figure 25-18Conversion of propionyl-CoA to succinyl-CoA. Page 922

  5. Figure 25-19The propionyl-CoA carboxylase reaction. Page 922

  6. Figure 25-20 The rearrangement catalyzed by methylmalonyl-CoA mutase. Page 923

  7. Figure 25-21Structure of 5’-deoxyadenosyl-cobalamin (coenzyme B12). Page 923

  8. Figure 25-23Proposed mechanism of methylmalonyl-CoA mutase. Page 926

  9. Figure 25-25Ketogenesis: the enzymatic reactions forming acetoacetate from acetyl-CoA. Page 929

  10. Figure 25-28 A comparison of fatty acid  oxidation and fatty acid biosynthesis. Page 931

  11. Figure 25-29 The phosphopantetheine group in acyl-carrier protein (ACP) and in CoA. Page 931

  12. Figure 25-30 Association of acetyl-CoA carboxylase protomers. Page 932

  13. Figure 25-31 Reaction cycle for the biosynthesis of fatty acids. Page 933

  14. Figure 25-32The mechanism of carbon–carbon bond formation in fatty acid biosynthesis. Page 934

  15. Chapter 27, Nitrogen Metabolism: 1. Deamination 2. Urea cycle 3. Conversion of aa carbon skeletons to common intermediates.

  16. First reaction in aa breakdown is always the removal of the -amino group. Most are transaminated to -KG which then transaminates OAA to asp. Transaminases require PLP (vit B6). Actual deamination to ammonia occurs via glu DH.

  17. Figure 26-1 Forms of pyridoxal-5’-phosphate.(a) Pyridoxine (vitamin B6) and (b) Pyridoxal-5’-phosphate (PLP) (c) Pyridoxamine-5’-phosphate (PMP) and (d) The Schiff base that forms between PLP and an enzyme -amino group.. Page 986

  18. Figure 26-2 The mechanism of PLP- dependent enzyme-catalyzed transamination. Page 987

  19. Nucleophillic attack by aa-NH3 on Schiff base. E-Lys now free to act as general base. Tautomerization encouraged by removal of the H of aa by E-Lys and protonation of PLP

  20. (see animated figure) Step II: Conversion back to PMP requires reverse of these 3 steps “An electron pusher’s delight: Cleavage of any of the aa’s C bonds produces a resonance stabilized carbanion whose e- are delocalized onto PLP (the electron sink).

  21. Figure 26-3 The glucose–alanine cycle. Muscle aminotransferases accept pyruvate as their amino acceptor. Overall scheme transfers nitrogen to liver for urea cycle. Page 988

  22. Figure 26-4 The oxidative deamination of glutamate by glutamate DH. GluDH is allosterically inhibited by GTP and NADH; Activated by ADP, leu, and NAD+.

  23. Nitrogen Excretory Products: Ammonia Uric Acid Urea

  24. Page 992 Figure 26-7The urea cycle.

  25. Figure 26-8 The mechanism of action of CPS I. Allosterically activated by N-acetyl glu: produced by NAGlu synthase--it is a sensor for [glu]. Page 993 Hi [glu] means lots of aa breakdown.

  26. Figure 26-9X-Ray structure of E. coli carbamoyl phosphate synthetase (CPS). Small subunit 3 sites very far away from each other: Connected by long tunnel “Channeling”! Page 993

  27. Ornithine Transcarbamoylase Carbamoyl Phosphate + Ornithine  Citrulline + Pi Ornithine produced in the cytosol must be transferred to mito by specific transport system. Citrulline is transferred back out to the cytosol Ornithine looks like Lys but has one fewer C’s Thus the side chain amino group is  !!!!

  28. Figure 26-10 The mechanism of action of argininosuccinate synthetase. Displacement Activation 18O label Mechanistic support Reaction type? Page 994 Condensation

  29. Arginosuccinase: Arginosuccinate  Arg + Fumarate

  30. Arginase: Arg + H2O  Ornithine + Urea

  31. Figure 26-11 Degradation of amino acids to one of seven common metabolic intermediates. Page 995

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