In the pentose pathway, which enzyme catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconolactone?

The conversion of glucose-6-phosphate to 6-phosphogluconolactone in the pentose phosphate pathway is catalyzed by glucose-6-phosphate dehydrogenase. This enzyme plays a critical role in the oxidative phase of the pathway, where it not only facilitates this specific conversion but also reduces NADP+ to NADPH in the process.

NADPH produced through this reaction is vital for various biosynthetic reactions and for maintaining the reduced state of glutathione in cells, which is crucial for protecting cellular components from oxidative damage. This reaction also marks the first committed step of the pentose phosphate pathway, steering glucose-6-phosphate into this pathway rather than through glycolysis.

Understanding this enzymatic conversion is fundamental to grasping how glucose is metabolized differently in various cellular contexts, particularly in scenarios where cells need NADPH for reductive biosynthesis or are engaged in nucleotide synthesis.