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PENTOSE PHOSPHATE(PHOSPHOGLUCONATE)
PATHWAYStudent Edition 5/30/13 VERSION
Pharm. 304 Biochemistry
Fall 2014
Dr. Brad Chazotte 213 Maddox Hall
Web Site:
http://www.campbell.edu/faculty/chazotte
Original material only ©2000-14 B. Chazotte
Goals
• Learn the Pentose Phosphate Pathway and its oxidative and non-oxidative phases.
• Learn what the Pentose phosphate pathway produces and how it can react to various metabolic demands (pathway modes of operation)
• Be familiar with the pathways that require pathway products.
• Understand the role of the transketolase and transaldolase reactions.
Pentose Phosphate ReactionOverall 3 Glucose-6-P + 6 NADP+ + 3 H2O
6 NADPH + 6 H+ + 3CO2 + 2F-6-P + GAP
Stage 1 3G-6-P + 6 NADP+ + 3 H2O 6 NADPH + 6 H+ + 3CO2
Stage 2 3Ru5P R5P + 2 Xu5P
Stage 3 R5P + 2Xu5P 2F6P + GAP
Voet & Voet 1995 Chap 21 p. 617-9
Berg, Tymoczko, & Stryer 2012 Table 20.4
Pathways That Require NADPH
Two key functions:
1. It provides all organisms with a source of NADPH to use on reductive biosynthesis
2. Generates pentose sugars, particularly ribose
Berg, Tymoczko, & Stryer 2002 Fig 20.19
PENTOSE PHOSPHATE PATHWAYOxidative Phase
Nonoxidative
Voet, Voet, & Pratt 2013 Figure 15.30
Berg, Tymoczko, & Stryer 2012 Table 20.3
Pentose Phosphate Pathway
Berg, Tymoczko, & Stryer 2012 Fig 20.19
Pentose Phosphate Pathway: Oxidative Phase
Voet, Voet, & Pratt 2013 Chap 15 p.508
Pentose Phosphate Pathway: Oxidative Phase Rx 1
Glucose 6-P Dehydrogenase Rx (#1)
Voet & Voet Biochemistry 1995 Fig. 21.24
Pentose Monophosphate Pathway
Voet, Voet & Pratt 2013 Figure 15.31
6-Phosphogluconate Dehydrogenase Rx (#3)
Berg, Tymoscko, & Stryer 2002 Fig 20.20b
Pentose Phosphate Pathway: Oxidative Phase Rx 2
Berg, Tymoscko, & Stryer 2012 Fig 20.19c
Pentose Phosphate Pathway: Oxidative Phase Rx 3
Linking the Pentose Phosphate and Glycolytic Pathways
[Transketolase & Transaldolase Rxs]
Linking the Pentose Pathway and Glycolysis
Transketolase
C5 + C5 C3 + C7
Transaldolase
C3 + C7 C6 + C4
Transketolase
C4 + C5 C6 + C3
Net Reaction
3 C5 2 C6 + C3 Berg, Tymoczko, & Stryer 2012 Chap 20
Lehninger 2000 Fig 15.21a
Nonoxidative Reactions of the Pentose Phosphate Pathway.
Lehninger 2000 Fig 15.21b
Schematic: 6 Pentoses to 5 Hexoses
Berg, Tymoczko, & Stryer 2012 Chao. 20 p. 603
Pentose Phosphate Pathway: Transketolase Rx
Pentose Phosphate Pathway: Transaldolase Rx
Berg, Tymoczko, & Stryer 2012 Chao. 20 p. 603
Pentose Phosphate Pathway: Transketolase Rx II
Berg, Tymoczko, & Stryer 2012 Chao. 20 p. 603
Transketolase & Transaldolase Mechanisms
Berg, Tymoscko, & Stryer 2002 Fig 20.23
Carbanion Intermediates
Voet, Voet & Pratt 2013 Fig 15.32
Pentose Phosphate Pathway: Transketolase Mechanism
KetoseSubstrate
AldoseProduct
KetoseProduct
Aldose Substrate
Pentose Phosphate Pathway: Transaldolase Mechanism
KetoseSubstrate
KetoseProduct
AldoseProduct
AldoseSubstrate
Voet, Voet & Pratt 2013 Fig 15.33
Berg, Tymoczko, & Stryer 2012 Table 20.3
Pentose Phosphate Pathway
Glycolytic & Pentose Phosphate Pathways Relationships
Voet, Voet & Pratt 2013 Figure 15.34
Berg, Tymoscko, & Stryer 2002 Fig 20.24
Four Modes of the Pentose Phosphate Pathway
Mode 1: 5 glucose-6-P + ATP 6 ribose-5-P + ADP + H+
Mode 2: glucose-6-P + 2NADP+ + H2O ribose-5-P + 2NADPH + 2H+ +CO2
Sum of Mode 3: glucose-6-P + 12NADP+ +7 H2O 6 CO2 + 12NADPH + 12H+ +Pi
Mode 4: 3 glucose-6-P + 6 NADP+ + 5 NAD+ + 5Pi + 8 ADP 5 pyruvate + 3 CO2 + 6 NADPH = 5 NADH + 8 ATP + 8H+ +2H2O
Berg, Tymoczko, & Stryer 2012 Table 20.4
Tissues with P.P. Pathway
End of Lectures
