Pentose Phosphate Pathway

Question 1

What are the two phases of PPP? What is the difference?

Answer 1

Oxidative stage for the creation of reducing agents (NADPH) and non-oxidative for movement of carbons to change sugars into usable conformations

Question 2

What is the key regulatory enzyme of the PPP, and how is it regulated?

Answer 2

G-6-P dehydrogenase; it is downregulated by NADPH, as fatty acid synthesis uses up NADPH, the enzyme becomes more active.

Question 3

What else regulates the PPP?

Answer 3

Cellular demands for R-5-P, NADPH, and energy. Depending on the needs of the cell, the PPP will shift the direction of products. PPP is a dynamic pathway.

Question 4

What is Glutathione? What are it’s two states?

Answer 4

a reducing agent comprised of 3 amino acids (yGlu-Cys-Gly)

Oxidized - where the sulfurs (Cysteines) of two glutathiones are bound together. Inactive in this state.

Reduced - the sulfur on the cysteine is bound to a hydrogen that is then used to reduce other molecules. Active in this state.

Question 5

What is G-6-P dehydrogenase deficiency?

Answer 5

a genetic (X-Linked Recessive) disorder that is characterized by a deficiency in the ability to produce NADPH. In oxidative states (e.g. under stress {infections}, NADPH lowering drugs {Malarial drugs}, or ingesting high oxidant foods {fava beans}), those with the disorder are very predisposed to developing hemolytic anemia due to inability of sufficient NADPH to repair RBC damage.

High prevelence in African American (11%), Mediterranean, and Asian populations.

Question 6

What are the purposes of the Pentose Phosphate pathway?

Answer 6

To produce NADPH (for use in fatty acid and steroid synthesis, and for regeneration of reduced glutathione)

To produce Ribose-5-Phosphate for nucleotide synthesis