Question

Which of the following is not the source of cytosolic NADPH ?

• A. Isocitrate dehydrogenase
• B. ATP citrate lyase
• C. Malic enzyme
• D. G6PD

Answer 1

The Correct Option is B

To determine which option is not a source of cytosolic NADPH, we need to understand the enzymes that contribute to the production of NADPH in the cell cytosol:

Enzyme	Role in NADPH Production
Isocitrate dehydrogenase	Uses the conversion of isocitrate to α-ketoglutarate in the cytosol to generate NADPH.
ATP citrate lyase	This enzyme catalyzes the conversion of citrate to acetyl-CoA and oxaloacetate. It does not directly produce NADPH.
Malic enzyme	Converts malate to pyruvate while generating NADPH in the process.
G6PD (Glucose-6-phosphate dehydrogenase)	The key enzyme in the pentose phosphate pathway, produces NADPH.

Based on this information, ATP citrate lyase does not produce NADPH in the cytosol. This enzyme's primary function is in the conversion of citrate, facilitating fatty acid synthesis, but it does not have a role in NADPH production. Therefore, the option that is not a source of cytosolic NADPH is ATP citrate lyase.