1 / 36

Enzymes-cofactors

Enzymes-cofactors. Dr. Mamoun Ahram. Resources. Biochemistry. 5th edition. Berg JM, Tymoczko JL, Stryer L. New York: W H Freeman; 2002. 8.1.1 Many Enzymes Require Cofactors for Activity http://www.ncbi.nlm.nih.gov/books/NBK22380/

Download Presentation

Enzymes-cofactors

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. Enzymes-cofactors Dr. Mamoun Ahram

  2. Resources • Biochemistry. 5th edition. Berg JM, Tymoczko JL, Stryer L. New York: W H Freeman; 2002. • 8.1.1 Many Enzymes Require Cofactors for Activity • http://www.ncbi.nlm.nih.gov/books/NBK22380/ • Section 9.2 Making a Fast Reaction Faster: Carbonic Anhydrases • http://www.ncbi.nlm.nih.gov/books/NBK22599/ • The Medical Biochemistry Pages • Introduction to Vitamins and Minerals • http://themedicalbiochemistrypage.org/vitamins.php

  3. Cofactors • What are cofactors? • What are coenzymes? • When are coenzymes called prosthetic groups and when are they cosubstrates?

  4. Classification of cofactors

  5. Apoenzymes vs. holoenzymes

  6. Vitamin derivatives as cofactors • What are vitamins? • Why are they important? • What are the two classes of vitamins?

  7. Vitamin C • Ascorbic acid • Example: prolyl hydroxylase • synthesizes 4-hydroxyproline (collagen) • An antioxidant

  8. Thiamin (vitamin B1) • Active form: thiamin pyrophosphate, TPP

  9. Pyruvate dehydrogenase complex • Decarboxylation of pyruvate into acetyl CoA by the pyruvate dehydrogenase complex

  10. α-ketoglutarate dehydrogenase • Decarboxylation of α-ketoglutarate into succinyl CoA by α-ketoglutarate dehydrogenase

  11. Riboflavin (vitamin B2) • The precursor for the coenzymes flavin adenine mononucleotide (FMD) and flavin adenine dinucleotide (FAD)

  12. Flavoproteins • Protiens that require FMN or FAD as cofactors • Redox reactions • FAD and FMN are prosthetic groups

  13. Succinate dehydrogenase • Oxidation of succinate into fumarate by succinate dehydrogenase

  14. Pyruvate dehydrogenase complex • FAD is a prosthetic group for the pyruvate dehydrogenase complex • It does not change in the overall reaction

  15. Niacin (vitamin B3) • Precursor of nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) • Cofactors for numerous dehydrogenases • Cosubstrates

  16. Pantothenic acid (vitamin B5) • Precursor of alanine and pantoic acid • Synthesis of coenzyme A (CoA) • Metabolism of carbohydrate, fats and proteins

  17. Coenzyme A • Coenzyme A transports acetyl groups from one substrate to another • via reactive thioester bond

  18. Pyruvate dehydrogenase complex • Decarboxylation of pyruvate into acetyl CoA by the pyruvate dehydrogenase complex

  19. Citrate synthase • Condensation of acetyl CoA and oxaloacetate into citrate by citrate synthase

  20. Pyridoxal phosphate (vitamin B6) • Pyridoxal, pyridoxamine and pyridoxine are precursors of active form • Metabolism of amino acids

  21. Aminotransferases • All aminotransferases contain the prosthetic group pyridoxal phosphate (PLP)

  22. Examples • Aspartate aminotransferase • Alanine aminotransferase

  23. Biotin • Carboxylation reactions

  24. Pyruvate carboxylase • condensation of CO2 to pyruvate forming oxaloacetate by pyruvate carboxylase

  25. Acetyl CoA carboxylase • Carboxylation of acetyl CoA to malonyl CoA by acetyl CoA carboxylase initiating fatty acid synthesis • Biotin is a prosthetic group

  26. Cobalamin (vitamin B12) • Composed of a tetrapyrrol ring structure and a cobalt ion in the center • Two significant reactions • linking fatty acid metabolism to sugar metabolism by rearranging methylmalonyl CoA to succinyl CoA • the formation of methionine from homocysteine by methylation

  27. Folic acid • Reduced within cells to tetrahydrofolate (THF) by dihydrofolate reductase (DHFR), an NADPH-requiring enzyme • THF derivatives carry and transfer of one carbon units during biosynthetic reactions, especially of nucleotides

  28. Lipoic acid • Not a dietary requirement in humans • Not a vitamin • A co-factor in pyruvate dehydrogenase and α-ketoglutarate dehydrogenase

  29. Metals

  30. Example

  31. الله معاكموكل عام وأنتم بخير

More Related