GLYCOLYSIS AND ALTERNATIVES BIOT 309 Fall 2013

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?

QUICK REVIEW EMP GLYCOLYSIS

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

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

ED PATHWAY * From G6P to KDG split enzymes are * * * * * < - - - 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 < - - * * < - - - * *  *

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

SIDE-BY-SIDE COMPARISON From G6P to KDG/KDPA split into G3P + pyruvate enzymes different

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

It’s a shunt

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.

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 Thiobacillus novellus and Brucella abortus

PATHWAY INTERMEDIATE USES

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

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

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

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

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, Enterococcus faecalis

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 Brucella abortus

Additional Topics

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

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

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

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