1 / 65

The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins

Chapter 24. The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins. Paula Yurkanis Bruice University of California, Santa Barbara. Cofactors. Many enzymes need a cofactor in order to catalyze a reaction. A cofactor can be a metal ion or an organic molecule.

iholden
Download Presentation

The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 24 The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins Paula Yurkanis Bruice University of California, Santa Barbara

  2. Cofactors Many enzymes need a cofactor in order to catalyze a reaction. A cofactor can be a metal ion or an organic molecule. A cofactor that is an organic molecule is called a coenzyme. Coenzymes are derived from vitamins.

  3. The Substrate and the Coenzyme are Bound to the Enzyme’s Active Site

  4. A Pyridine Nucleotide Coenzyme is Needed for Many Redox Reactions NAD+ and NADP+ are oxidizing agents. NADH and NADPH are reducing agents.

  5. NAD+ is the Most Common Oxidizing Agent NADPH is the Most Common Reducing Agent

  6. NAD+ is Composed of Two Nucleotides Linked Together by Their Phosphate Groups NAD+ = nicotinamide adenine dinucleotide The nicotinamide nucleotide is derived from vitamin B3. The adenine nucleotide is derived from ATP.

  7. ATP

  8. Metabolism Metabolism = the reactions cells carry out to obtain the energy they needand to synthesize the compounds they require. Metabolism can be divided into two parts. catabolism: complex molecule simple molecules + energy anabolism: simple molecules + energy complex molecule

  9. NAD+ is an Oxidizing Agent A dehydrogenase is an enzyme that catalyzes an oxidation reaction. NAD+ and NADH are used in catabolic reactions. Catabolic reactions are primarily oxidation reactions, so NAD+ is the most common oxidizing agent. NADP+ and NADPH are used in anabolic reactions. Anabolic reactions are primarily reduction reactions, so NADPH is the most common reducing agent.

  10. NADPH is a Reducing Agent

  11. The Mechanism for Oxidation All the chemistry of the pyridine nucleotide coenzymes takes place at the 4-position of the pyridine ring.

  12. Glyceraldehyde-3-Phosphate Dehydrogenase Glyceraldehyde-3-phosphate dehydrogenase is an example of an enzyme that uses NAD+ as an oxidizing agent.

  13. The Mechanism

  14. The Mechanism for Reduction All the chemistry of the pyridine nucleotide coenzymes takes place at the 4-position of the pyridine ring.

  15. Most Enzyme-Catalyzed Reactions are Highly Selective The oxidizing enzyme can distinguish between the two hydrogens of ethanol. Only Ha is removed.

  16. Most Enzyme-Catalyzed Reactions are Highly Selective The reducing enzyme can distinguish between the two hydrogens of NADH. Only Ha is transferred.

  17. FAD is an Oxidizing Agent FAD = flavin adenine dinucleotide

  18. FAD-Catalyzed Reactions Most oxidation reactions catalyzed by FAD do not involve a carbonyl group.

  19. FAD is Reduced to FADH2 FAD is an oxidizing agent. FADH2 is a reducing agent.

  20. The Mechanism forDihydrolipoate Dehydrogenase

  21. The Mechanism forSuccinate Dehydrogenase

  22. The Mechanism for D- or L-Amino Oxidase

  23. Unlike NAD+ and NADH, FAD and FADH2 Do Not Dissociate From the Enzyme NAD+ is required to reoxidize the reduced cofactor.

  24. Thiamine Pyrophosphate (TPP) TPP is the coenzyme required by enzymes that catalyze the transfer of an acyl group.

  25. A Reaction That Requires TPP

  26. The Reactive Part of TPP The TPP ylide is a good nucleophile. All enzyme-catalyzed reactions that require TPP start by forming an enamine.

  27. The Mechanism forPyruvate Decarboxylase

  28. The Pyruvate Dehydrogenase Complex The conversion of pyruvate to acetyl-CoA requires five coenzymes: TPP, lipoate, coenzyme A, FAD, and NAD+.

  29. Part Two of the Mechanism Part one of the mechanism is the reaction of the TPP ylide with pyruvate to form the same enamine that is formed from the reaction of the TPP ylide with pyruvate by pyruvate carboxylase. Lipoate is attached to its enzyme by forming an amide with a lysine side chain.

  30. Part Three of the Mechanism

  31. Coenzyme A

  32. Biotin Biotin is required by enzymes that catalyze the carboxylation of a carbon adjacent to a carbonyl group. Biotin is attached to its enzyme by forming an amide with a lysine side chain.

  33. Enzymes That Require Biotin

  34. Activating Bicarbonate Biotin-requiring enzymes require Mg2+ and ATP.

  35. Mechanism for Carboxylation

  36. Pyridoxal Phosphate (PLP) Pyridoxal phosphate is attached to its enzyme by formingan imine with a lysine side chain.

  37. PLP Catalyzes Reactions of Amino Acids

  38. PLP Catalyzes Reactions of Amino Acids

  39. PLP Catalyzes Reactions of Amino Acids

  40. The Amino Acid Becomes Attached to PLP by Transimination In the reactant, the imine is between PLP and a lysine side chain of the enzyme. In the product, the imine is between PLP and the amino acid.

  41. The First Step in All PLP-Catalyzed Reactions The first step of the enzyme-catalyzed reactions isbreaking a bond attached to the alpha-carbon.

  42. The Mechanism for Decarboxylation

  43. The Mechanism for Racemization

  44. The Mechanism for Transamination (Part 1)

  45. The Mechanism for Transamination (Part 2)

  46. Coenzyme B12

  47. Enzyme-Catalyzed Reactions That Require B12 Enzymes that catalyze certain rearrangement reactions require coenzyme B12.

  48. Y and H Change Places In an enzyme-catalyzed reaction that requires coenzyme B12, a group (Y) bonded to one carbon changes places with a hydrogen bonded to an adjacent carbon.

  49. The Mechanism for a Reaction that Requires B12

More Related