Synonyms

Pentose phosphate pathway
Dickens Horecker pathway
Phosphogluconate pathway
Shunt pathway
Warburg Dickens Lipman pathway

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An alternative pathway to glycolysis and TCA cycle for the oxidation of glucose. It is more anabolic in nature and all reactions occur in the cytosol.
About 10% of glucose molecule per day are entering in this pathway.
Liver and RBC metabolize about 30% glucose by this pathway.
Consists of an oxidative and a nonoxidative phase.

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OXIDATIVE PHASE:

Glucose 6 phosphates oxidised by NADP+ dependent glucose 6 phosphate dehydrogenase to 6 phospho gluconolactone.1 molecule NADPH formed.
Lactone hydrolyzed by gluconolactone hydrolase to 6 phosphoglucose acid.
An oxidative step coupled with decarboxylation. The enzyme is 6 phosphogluconate dehydrogenase. Ribulose 5 phosphate is formed .2nd molecule of NADPH generated and a molecule of CO2.

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NONOXIDATIVE PHASE

Pentose phosphate is converted to intermediates of glycolysis.
Two enzymes transketolase and transaldolase catalyze the reactions.

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SIGNIFICANCE OF HMP SHUNT

1. NADPH generated is required for reductive biosynthesis of fatty acids, cholesterol and steroids.
2. Free radical scavenging.
3. NADPH required for erythrocyte membrane integrity- keep glutathione in a reduced state.
4. Prevention of met-hemoglobinemia
5. Detoxification of drugs.
6. NADPH required for preserving the transparency of the lens.
7. Macrophage bacterial activity

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ABNORMALITY OF HMP SHUNT

1. Glucose 6 phosphate dehydrogenase deficiency- results in hemolytic anaemia, neonatal jaundice& kidney failure.
2. Deficiency of transaldolase - results in liver cirrhosis and male infertility.
3. Wernicke Korsakoff syndrome- alteration in transketolase.