PENTOSE PHOSPHATE
(PHOSPHOGLUCONATE)
PATHWAY
Student Edition
5/30/13 VERSION
Dr. Brad Chazotte
213 Maddox Hall
chazotte@campbell.edu
Web Site:
http://www.campbell.edu/faculty/chazotte
Original material only ©2000-14 B. Chazotte
Pharm. 304
Biochemistry
Fall 2014
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 Reaction
Overall
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
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 2012 Table 20.4
PENTOSE PHOSPHATE PATHWAY
Oxidative Phase
Nonoxidative
Berg, Tymoczko, & Stryer 2002 Fig 20.19
Voet, Voet, & Pratt 2013 Figure 15.30
Pentose Phosphate Pathway
Berg, Tymoczko, & Stryer 2012 Table 20.3
Pentose Phosphate Pathway: Oxidative Phase
Berg, Tymoczko, & Stryer 2012 Fig 20.19
Pentose Phosphate Pathway: Oxidative Phase Rx 1
Voet, Voet, & Pratt 2013 Chap 15 p.508
Glucose 6-P Dehydrogenase Rx (#1)
6-Phosphogluconate Dehydrogenase Rx (#3)
Voet & Voet Biochemistry 1995 Fig. 21.24
Pentose Monophosphate
Pathway
Voet, Voet & Pratt 2013 Figure 15.31
Pentose Phosphate Pathway: Oxidative Phase Rx 2
Berg, Tymoscko, & Stryer 2002 Fig 20.20b
Pentose Phosphate Pathway: Oxidative Phase Rx 3
Berg, Tymoscko, & Stryer 2012 Fig 20.19c
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
Nonoxidative Reactions of the Pentose Phosphate Pathway.
Lehninger 2000 Fig 15.21a
Schematic: 6 Pentoses to 5 Hexoses
Lehninger 2000 Fig 15.21b
Pentose Phosphate Pathway: Transketolase Rx
Berg, Tymoczko, & Stryer 2012 Chao. 20 p. 603
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
Carbanion Intermediates
Berg, Tymoscko, & Stryer 2002 Fig 20.23
Pentose Phosphate Pathway: Transketolase Mechanism
Ketose
Substrate
Ketose
Product
Aldose
Product
Aldose
Substrate
Voet, Voet & Pratt 2013 Fig 15.32
Pentose Phosphate Pathway: Transaldolase Mechanism
Aldose
Product
Ketose
Substrate
Ketose
Product
Aldose
Substrate
Voet, Voet & Pratt 2013 Fig 15.33
Pentose Phosphate Pathway
Berg, Tymoczko, & Stryer 2012 Table 20.3
Glycolytic & Pentose Phosphate
Pathways Relationships
Voet, Voet & Pratt 2013 Figure 15.34
Four Modes of the Pentose Phosphate Pathway
Mode 1:
Mode 2:
Sum of Mode 3:
Mode 4:
5 glucose-6-P + ATP
6 ribose-5-P + ADP + H+
glucose-6-P + 2NADP+ + H2O
ribose-5-P + 2NADPH + 2H+ +CO2
glucose-6-P + 12NADP+ +7 H2O
6 CO2 + 12NADPH + 12H+ +Pi
3 glucose-6-P + 6 NADP+ + 5 NAD+ + 5Pi + 8 ADP
5 pyruvate + 3 CO2 + 6 NADPH = 5 NADH + 8 ATP + 8H+ +2H2O
Berg, Tymoscko, & Stryer 2002 Fig 20.24
Tissues with P.P. Pathway
Berg, Tymoczko, & Stryer 2012 Table 20.4
End of Lectures