GLYCOLYSIS AND ALTERNATIVES

1. GLYCOLYSIS AND ALTERNATIVES BIOT 309 Fall 2013

2. GLYCOLYSIS AND ALTERNATIVES • Bacteria use 3 different pathways to convert glucose to PGA (3-phosphoglycerate) (see diagram) • Embden-Myerhoff (shown in next slide) • Entner-Dordoroff (ED) Pathway • Pentose phosphate pathway (shunt)/hexose monophosphate shunt Energy yields are different. What are they?

3. QUICK REVIEW EMP GLYCOLYSIS

4. ENTNER-DUODOROFF PATHWAY • Uses EMP pathway for some steps • Unique enzymes and intermediates

5. ED PATHWAY* * Be aware that this figure does not show ATP use or production since enzymes from EMP pathway perform these reactions.

6. ED PATHWAY • Glucose begins pathway • E yield = 1 ATP + 1 NADH + 1 NADPH • *From G6P to KDG split enzymes are • different • Pyruvate formation • Directly  • Indirectly – G3P enters EMP < - - * * < - - - *  * *

7. Entner Duodoroff Pathway What do abbreviations stand for? MAKE a list!!!

8. SIDE-BY-SIDE COMPARISON From G6Pto KDG/KDPA split into G3P + pyruvate enzymes different

9. THIRD GLYCOLYSIS PATHWAY Pentose Phosphate Pathway (PPP) = Hexose Monophosphate Pathway (HMP) = Phosphogluconate Pathway Sometimes called a shunt. • Operates at same time as EMP

10. It’s a shunt

11. PPP is a shunt • The pathway begins with the glycolytic intermediate glucose 6-P. • It reconnects with glycolysis because two of the end products of the PPP are glyceraldehyde 3-P and fructose 6-P; two intermediates further down in the glycolytic pathway. • It is for this reason that the PPP is often referred to as a shunt.

12. PPP • Provides ribose-5-phosphate = precursor to ribose and deoxyribose in nucleic acids • Provides erythrose phosphate = precursor for synthesis of aromatic amino acids • Other intermediates used in other pathways • Provides NADPH – major source of energy for anabolic reactions, e.g., nucleic acids, lipids • Used exclusively by Thiobacillusnovellus and Brucellaabortus

13. PATHWAY INTERMEDIATE USES

14. 1st Reaction High [NADPH] inhibits allosterically High [NADP+] stimulates allosterically irreversible irreversible

15. MAKES SUGARS WITH DIFFERENT CARBON NUMBERS 2 enzymes convert ribuloe-5-Pi to a ketose and an aldose both with 5 C All reversible Transketolase 1 2 5C 1 7C + 1 3C Transketolase 2 1 7C +1 3C  4C+6C Transketolase 3 4C+5C  6C + 3C

16. Transketolase • Requires thiamine diphosphate (TDP) and Mn2+ as co-factors • TDP (TPP) is needed for redox

17. Regulation • G-6-P is partitioned between EMP and PPP • Depends on • NADP+ and NADPH concentrations • NADP+ high favors EMP • NADPH high favors PPP

18. ENTNER-DUDOROFF PATHWAY • The Entner-Doudoroff pathway yields one ATP and two NADPH molecules from one glucose molecule. • Uses 4 enzymes that are different from EMP 1 Glucose 2 pyruvate + 1 ATP + 1 NADH + 1 NADPH Bacteria: Pseudomonas, Rhizobium, Azotobacter, Agrobacterium, Enterococcusfaecalis

19. PENTOSE PHOSPHATE SHUNT PATHWAY • Precursors to the ribose and deoxyribose in nucleic acids • Provides erythrose phosphate which is a precursor for synthesis of aromatic amino acids • reducing power = NADPH Overall Oxidative Reaction: 1 Glucose 6 – P + 2 NADP+ + 1 H2O  1 Ribose 5-P + 1 CO2+ 2 NADPH + 2 H+ Non-Oxidative Reactions • change number of carbons in sugar molecules • make intermediates used in other biosynthetic pathways including feeding back into PPP and EMP Used exclusively by Thiobacillus novellus and Brucellaabortus

21. Additional Topics

22. Coenzyme A • CoASH • Free SH • role in TCA • alpha KG -> succinyl CoA

23. Coenzyme A • = acyl group carrier, donates acyl group to other molecules • Acetyl = acetyl CoA • Succinyl = succinyl CoA • Roles in • Oxidation of pyruvate in TCA • Synthesis and oxidation of fatty acids

24. Acetyl Coenzyme A Structure * * What is this? Vitamin B5

25. END