1. Organic Chemistry 4 th Edition Paula Yurkanis Bruice Chapter 25 The Organic Mechanisms of the Coenzymes Metabolism Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall

3. catabolism: complex molecules simple molecules + energy anabolism: simple molecules + energy complex molecules Overall View of Metabolism

4. The Four Stages of Catabolism

5. The coenzymes most commonly used by enzymes to catalyze redox reactions: oxidizing agents reducing agents

7. The Components of NAD +

8. Oxidation of an Alcohol by NAD +

9. Reduction by NADH

10. All the chemistry of the pyridine nucleotide coenzymes takes place at the 4-position of the pyridine ring

13. The Mechanism of Reduction by NADH (or NADPH)

14. A reducing enzyme can distinguish between the two hydrogens at the 4-position of the nicotinamide ring

15. Another set of coenzymes in redox reactions

18. Mechanisms for Flavin Nucleotide Coenzymes

21. Unlike NADH, FADH 2 does not dissociate from the enzyme

22. The Coenzyme Form of Vitamin B 1

24. Consider this reaction …

28. Biotin: Vitamin H

30. In addition to requiring bicarbonate, biotin-requiring enzymes require Mg 2+ and ATP

32. Pyridoxal Phosphate: Vitamin B 6 Required by enzymes that catalyze certain transformations of amino acids

33. In each of these transformations, one of the bonds to the  -carbon of the amino acid substrate is broken in the first step of the reaction

41. In the PLP-dependent reactions, the bond cleaved in the first step of the reaction depends on the conformation of the amino acid that the enzyme binds

42. Enzymes that catalyze certain rearrangement reactions require coenzyme B 12

45. Tetrahydrofolate is the coenzyme required by enzymes that catalyze the transfer of a group containing one carbon to their substrates

46. The Six Different THF-Coenzymes

48. The Enzyme that Converts U’s into T’s

50. Conversion of Dihydrofolate Back to N 5, N 10 -Methylene-THF

51. 5-Fluorouracil is a mechanistic-based inhibitor of thymidylate synthase used in cancer chemotherapy

52. Aminopterin and methotrexate competitively inhibit dihydrofolate reductase and are used as anticancer drugs

53. Vitamin K is required for proper clotting of blood

57. Regeneration of Vitamin KH 2