Pentose phosphate pathway Flashcards
Glucose 6 Phosphate Dehydrogenase
Forms 6 phosphogluconolactone and NADPH from glucose 6 phosphate
Irreversible
Main regulatory step in pentose phosphate pathway
fate of 6 phosphogluconolactone
hydrolized quickly to 6 phosphogluconate
6 phosphogluconate Dehydrogenase
Forms Robulose 5 Phosphate, CO2, and NADPH from 6 phosphoguconate
Irreversible
Oxidative phase of pentose phosphate pathway
Transketolase
Enzyme in the nonoxidative phase of the pentose phosphate pathway.
Catalyzes two reactions with TPP as a coenzyme
1) xyulose 5 P and Ribose 5 P to glyceraldehyde 3 phosphate and sedoheptulose 7 P
2) Erythrose 4 P and another xyulose 5 P to form Fructose 6 P and glyceraldehyde 3 P
Transaldolase
Enzyme in the nonoxidative phase of the pentose phosphate pathway.
Takes glyceraldehyde 3 P formed in an earlier step and sedoheptulose 7 P and forms Fructose 6 P and Erythrose 4 P
NADPH
Formed in the Pentose Phosphate Pathway as a major source.
Used for fatty acid and steroid synthesis (liver and adipose tissue)
Detoxification of H2O2 using glutathione (erythrocytes)
Used in phagocytosis properties in white blood cells
Used in the synthesis of NO
Glucose 6 phosphate deficiency
x - linked recessive disorder
Diminished ability to form NADPH resulting in reduced glutathione pool resulting in accumulation of H2O2 damaging the cell membrane and causing hemolysis of RBC.
Can also lead to denatured proteins forming Heinz bodies
Most severe in RBC as Pentose P Pathway is the only source of NADPH
Purpose of pentose phosphate pathway
NADPH formation for cellular processes
Pentoses for nucleic acid synnthesis
Glutathion Peroxidase
converts H2O2 and 2 glutathiones to form 2 molecules of H2O. (the 2 glutathiones are bound together by disulfide bonds)
Glutathione reductase
Replenished glutatione by breading the disulfide bond formed during H2O2 detoxification.
requires the oxidation of NADPH + H
