Hexose Monophosphate
Hexose Monophosphate
Pentose Phosphate Pathway
 Glycolysis, TCA, and oxidative phosphorylation are primarily
concerned with the generation of ATP.
 The PPP meets the need of all organisms for a source of
NADPH to use in reductive biosynthesis.
 The reducing power is NADPH.
 There is a fundamental distinction
NADH 
NADPH 
The direction of HMP depends on the supply and demand for
intermediates in the cycle…
Two Major Functions
1.
2.
NADPH
Ribose
Overall reaction:
3G-6-P + 6NADP+  3CO2 + 2G-6-P + Glyceraldehyde-3P + 6NADPH + 6H+

It occurs in the cytosol because NADP+ is used as a hydrogen
acceptor.
There are two sequential reactions.
1. Oxidative
2. Nonoxidative
Oxidative and Nonoxidative Reactions

In oxidative, G-6-P undergoes dehydrogenation and
decarboxylation to give a pentose ribulose-5-P.

In nonoxidative, ribulose 5-P is converted back to
G-6-P by a series of reactions involving two
enzymes
1. Transketolase
2. Transaldolase

Dehydrogenation of G-6-P is the major biological
control of the HMP.

G-6-PD is strongly inhibited by NADPH.
Oxidative Branch