burning question about G6PD deficiency

[FrauBlucher]

Dunno if this has been confusing anyone else, but everytime it comes up I go in circles.

Ok, so G6PD - makes NADPH in the HMP shunt. Good. Then the NADPH is oxidized by NADPH oxidase leading to the respiratory burst. Also good. Deficiency of NADPH oxidase causes chronic granulomatous disease. BUT! G6PD deficiency doesn't cause CGD. I just figured that we make NADPH elsewhere, so G6PD deficiency doesn't affect the respiratory burst, but I just got a QBank question that says (in the answer explanation): "Thus, if G6PD is inactive, NADPH cannot be generated, and NADPH oxidase is also inhibited."

Help?

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[blz]

I'll take a stab at it.

G6PD deficiency isnt' a complete absence of the enzyme, it's an decrease in the half life of the enzyme. So under non stressed conditions you are ok and can make some NADPH. So you wouldn't have a constant CGD state. I'd imagine though, if you were undergoing an acute hemolytic episode, you would be more susceptible to infections without a functioning NADPH oxidase.

 

[cubsrule4e]

maybe you should just put some ice on it

 

[WhoisJohnGalt]

Dunno if this has been confusing anyone else, but everytime it comes up I go in circles.

Ok, so G6PD - makes NADPH in the HMP shunt. Good. Then the NADPH is oxidized by NADPH oxidase leading to the respiratory burst. Also good. Deficiency of NADPH oxidase causes chronic granulomatous disease. BUT! G6PD deficiency doesn't cause CGD. I just figured that we make NADPH elsewhere, so G6PD deficiency doesn't affect the respiratory burst, but I just got a QBank question that says (in the answer explanation): "Thus, if G6PD is inactive, NADPH cannot be generated, and NADPH oxidase is also inhibited."

Help?

p. 6 of 26 of Goljan's RR Path: "Deficiency of NADPH (e.g. G6PD deficiency) produces a microbicidal defect." Way to make the connection!! 😀

 

[peter90036]

i was going to ask a similar questoin,

if you got G6PD deficiency, why dont you get CGD (i was wondering if G6PD for RBCs was coded on the same place as that for neutrophils...)

googled into: profound G6PD deficiency will lead to a decrease in NADPH oxidase, and a CGD-like presentation.

 

[ZonaRidicularis]

z

 

[peter90036]

(forgot):
the other source of NADPH, which i guess can be used instead of HMP /G6PD deficit

fatty acid synthesis

Malate + NADP --*--> Pyruvate + NADPH

* = malic enzyme (cytosol)

i suppose RBC's don't have a reason to make FA ... since they focus on carrying oxygen 😛

 

[ZonaRidicularis]

z