Final answer:
Glucose-6-phosphate dehydrogenase is the key regulatory enzyme in the pentose phosphate pathway. It catalyzes the conversion of glucose-6-phosphate into 6-phosphogluconolactone and is primarily regulated by NADP+/NADPH levels in the cell.
Step-by-step explanation:
Glucose-6-phosphate dehydrogenase (G6PD) is the key regulatory enzyme in the pentose phosphate pathway. It catalyzes the conversion of glucose-6-phosphate (G6P) into 6-phosphogluconolactone.
G6PD deficiency, a genetic condition resulting in a shortage of G6PD, is the most common enzyme deficiency in humans. G6PD regulates the production of NADPH, a coenzyme that plays a crucial role in cellular redox reactions and provides reducing power to cells.
G6PD is primarily regulated by the level of NADP+ and NADPH in the cell. When the cellular energy state is high and NADPH levels are sufficient, G6PD is inhibited, slowing down the pentose phosphate pathway. Conversely, when the energy state is low and NADPH levels are low, G6PD is activated, promoting the production of NADPH.