GLYCOLYSIS AND ALTERNATIVES BIOT 309 Fall 2013 GLYCOLYSIS
GLYCOLYSIS AND ALTERNATIVES BIOT 309 Fall 2013
GLYCOLYSIS AND ALTERNATIVES • Bacteria use 3 different pathways to convert glucose to PGA (3 -phosphoglycerate) (see diagram) 1. Embden-Myerhoff (shown in next slide) 2. Entner-Dordoroff (ED) Pathway 3. 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 • Glucose begins pathway • E yield = 1 ATP + 1 NADH + 1 NADPH • * From G 6 P to KDG split enzymes are different • Pyruvate formation • Directly • Indirectly – G 3 P enters EMP < - - * * <--- * * *
Entner Duodoroff Pathway What do abbreviations stand for? MAKE a list!!!
SIDE-BY-SIDE COMPARISON From G 6 P to KDG/KDPA split into G 3 P + 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
1 st Reaction High [NADPH] inhibits allosterically irreversible High [NADP+] stimulates allosterically irreversible
MAKES SUGARS WITH DIFFERENT CARBON NUMBERS All reversible 2 enzymes convert ribuloe-5 -Pi to a ketose and an aldose both with 5 C Transketolase 1 2 5 C 1 7 C + 1 3 C Transketolase 2 1 7 C +1 3 C 4 C+6 C Transketolase 3 4 C+5 C 6 C + 3 C
Transketolase • Requires thiamine diphosphate (TDP) and Mn 2+ 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 H 2 O 1 Ribose 5 -P + 1 CO 2+ 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 • Co. ASH • Free SH • role in TCA alpha KG -> succinyl Co. A
Coenzyme A • = acyl group carrier, donates acyl group to other molecules – Acetyl = acetyl Co. A – Succinyl = succinyl Co. A • Roles in – Oxidation of pyruvate in TCA – Synthesis and oxidation of fatty acids
Acetyl Coenzyme A Structure * * What is this? Vitamin B 5
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