Enzymes

Question 1

Here is a detailed explanation of the main coenzymes and their roles:

Energy Transfer Coenzymes

1. ATP (Adenosine Triphosphate)

Function: Universal energy currency; transfers phosphate groups to drive endergonic reactions.

Pathways: Glycolysis, TCA cycle, oxidative phosphorylation.

2. GTP (Guanosine Triphosphate)

Function: Energy source for protein synthesis and signaling pathways.

Pathways: TCA cycle (succinyl-CoA synthetase), gluconeogenesis.

3. Coenzyme A (CoA)

Function: Transfers acyl groups; central in fatty acid metabolism.

Pathways: Fatty acid oxidation, TCA cycle (acetyl-CoA formation).

Electron Transfer Coenzymes

4. NAD⁺ (Nicotinamide Adenine Dinucleotide)

Function: Electron acceptor in catabolic reactions (oxidation of glucose and fatty acids).

Pathways: Glycolysis, TCA cycle, oxidative phosphorylation.

5. NADH

Function: Reduced form of NAD⁺; donates electrons to the electron transport chain.

6. NADP⁺ (Nicotinamide Adenine Dinucleotide Phosphate)

Function: Involved in anabolic reactions (e.g., lipid and nucleotide synthesis).

Pathways: Pentose phosphate pathway.

7. NADPH

Function: Reducing agent for biosynthesis (e.g., fatty acids) and antioxidant defense.

8. FAD (Flavin Adenine Dinucleotide)

Function: Electron acceptor in redox reactions.

Pathways: TCA cycle (succinate dehydrogenase), beta-oxidation.

9. FADH₂

Function: Reduced form of FAD; donates electrons to the electron transport chain.

10. FMN (Flavin Mononucleotide)

Function: Electron carrier.

Pathways: Part of Complex I in the electron transport chain.

11. Ubiquinone (Coenzyme Q)

Function: Lipid-soluble electron carrier in the electron transport chain.

Pathways: Transfers electrons between Complexes I/II and III.

Carbon Transfer Coenzymes

12. THF (Tetrahydrofolate)

Function: Transfers one-carbon units in nucleotide and amino acid metabolism.

Pathways: DNA synthesis, methionine cycle.

13. Biotin

Function: Transfers carboxyl groups in carboxylation reactions.

Pathways: Pyruvate carboxylase, acetyl-CoA carboxylase.

14. S-Adenosylmethionine (SAM)

Function: Donates methyl groups.

Pathways: Methylation of DNA, RNA, and proteins.

Aldehyde Transfer Coenzyme

15. TPP (Thiamine Pyrophosphate)

Function: Transfers aldehyde groups in decarboxylation and transketolase reactions.

Pathways: Pyruvate dehydrogenase, pentose phosphate pathway.

Amino Group Transfer Coenzyme

16. PLP (Pyridoxal Phosphate)

Function: Transfers amino groups in amino acid metabolism.

Pathways: Transamination, deamination, decarboxylation.

Hydroxylation Coenzyme

17. Ascorbic Acid (Vitamin C)

Function: Assists in hydroxylation of proline and lysine residues in collagen synthesis.

Isomerization Coenzyme

18. Cobalamin (Vitamin B12)

Function: Assists in isomerization and methyl group transfer.

Pathways: Methionine synthesis, odd-chain fatty acid metabolism.

Heme-Containing Coenzymes

19. Heme

Function: Transfers electrons in cytochromes and hemoglobin.

Pathways: Electron transport chain, oxygen transport.

Light Absorption Coenzyme

20. Retinal

Function: Involved in vision by absorbing light.

Pathways: Phototransduction in the retina.

Other Specialized Coenzymes

21. Lipoamide

Function: Transfers acyl groups and electrons in multi-enzyme complexes.

Pathways: Pyruvate dehydrogenase, α-ketoglutarate dehydrogenase.

22. Coenzyme M

Function: Involved in methane biosynthesis.

Pathways: Methanogenesis in archaea.

23. PQQ (Pyrroloquinoline Quinone)

Function: Acts as a redox cofactor in bacteria.

Would you like a diagram, a pathway connection, or further explanation for any specific coenzyme?