Pentose Phosphate Pathway Flashcards
Pentose Phosphate Pathway
Hexose Monophosphate Shunt
Dicken Horecker Pathway
Phosphogluconate Pathway
Site of Pentose Phosphate Pathway
RBCs and tissues that produce lipids (liver, adipose tissues, adrenals, testes, lactating mammaries)
Cytosol
Rate limiting step in Pentose Phosphate Pathway
Glucose 6 Phosphate Dehydrogenase
Biochemical Significances of HMP Pathway
Alternative route for metabolism of glucose
Complete oxidation of glucose
MAJOR FUNCTION - NADPH and RIBOSE
NO ATP is PRODUCED NOR CONSUMED
Substrate of Pentose Phosphate Pathway
Glucose 6-Phosphate
Important Products of Pentose Phosphate Pathway
NADPH
Ribose 5 phosphate
Rate Limiting Step of Pentose Phosphate Pathway
Glucose 6-Phosphate Dehydrogenase
Uses of NADPH
Prevent oxidative damage - RBC, lens by keeping glutathione in the reduced state
Reductive biosynthesis of FA and steroids
Key Enzyme in the 1st Phase of HMP (Oxidative - irreversible)
Glucose-6 Phosphate Dehydrogenase
Products of the 1st Phase of HMP (Oxidative - irreversible)
2 NADPH
Ribulose 5-phosphate
Key Enzyme in the 2nd Phase of HMP (Non-oxidative - reversible)
Transketolase
(Cofactor: Thiamine)
Transaldolase
Products of the 2nd Phase of HMP (Non-oxidative - reversible)
Ribose-5-phosphate
Fructose-6-phosphate
Glyceraldehyde 3-phosphate
MC enzyme deficiency in human beings
X-linked recessive
Glucose-6 Phosphate Dehydrogenase (G6PD) Deficiency
hemolytic anemia
methemoglobinemia
d.t. decrease in NADPH which clears the free radicals in the RBCs and keep the iron the hemoglobin in the reduced state
People with Glucose-6 Phosphate Dehydrogenase (G6PD) Deficiency are sensitive to:
CERTAIN DRUGS - Primaquine, Aspirin, Sulfadrugs
Consumption of fava beans - can also precipitate hemolysis
Functions of Pentose Phosphate Pathway
Reductive biosynthesis of fatty acids and steroids
Glutathione reduction inside RBCs
Cytochrome P450 monooxygenase system
Oxygen dependent bactericidal mechanism of WBCs
Synthesis of Nitric Oxide
Reduced glutathione removes H2O2 in a reaction catalyzed by
GLUTATHIONE PEROXIDASE
Reduced glutathione is regenerated by
GLUTATHIONE REDUCTASE (requires NADPH)
MC disease producing enzyme abnormality in humans
involves DECREASED NADPH in RBCs and DECREASED activity of glutathione reductase –> free radicals and peroxidase accumulation
Glucose 6 Phosphate Dehydrogenase Deficiency (G6PD)
hemolytic anemia after oxidative stress - d.t. poor RBC defense against oxidizing agents
HEINZ BODIES
Altered hemoglobin that precipitates within RBCs
HEINZ BODIES
Abnormally shaped RBCs d.t. phagocytic removal of Heinz bodies in spleen
BITE CELLS
Deficiency in NADPH oxidase
Chronic Granulomatous Disease
severe persistent and chronic pyogenic infections
