pentose phosphate pathway - wou homepagewou.edu/~guralnl/gural/451pentose phosphate...

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