Pentose Phosphate Pathway• Overview• Oxidative branch• Non-oxidative• Modes• Red Blood cells• Glucose 6-P
dehydrogenasedeficency
• White blood cells
Overview • oxidizes Glucose • located in cytoplasm • produce NADPH and
Ribose 5-P • occurs adipose,
mammary, ovary, testes, adrenal gland – can account for over 30%
of flux of glucose • Two parts
– oxidative – non-oxidative
Oxidative branch
• Three steps • Glucose 6-P
dehydrogenase is committing step
• Produces 2 NADPH, 1 CO2, 1 Ribose 5-P
• Fourth step is isomerase of Ribulose to Ribose
Glu 6-P + 2NADP+ H2O ribose 5-P + 2NADPH + CO2 + H+
Non-oxidative Branch
• Reversible • Interconverts
3,4,5,6,7 carbon sugars for synthesis of other compounds
• Transketolase• Transaldolase
Steps: Non-oxidative Branch
Transketolase
Transaldolase
Summary
Modes of Pentose Pathway
Role of Pentose Pathway
Red Blood cells
• detoxify oxidation products
• reduce sulfhydralgroups
• Keep Fe+2
• maintain structure of RBC
Mechanism
• NADPH reduces Glutathione
• Glutathione reductasecatalyses reaction
• Peroxide inactivation
Role of Glutathione
Glucose 6-P dehydrogenasedeficency
• sex-linked trait • cause oxidative stress under
certain environmental conditions
• low levels of glutathione • another genetic trait favored
in malarial regions • distorts surface of red blood
cells • targets them for destruction • anit-malarial drugs cause
hemolytic crisis by oxdiativestress
White blood cells
• generates oxidizing agents
• NADPH oxidase• phagolysosomes and
myeloperoxidase
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