What is the activity of isocitrate dehydrogenase increased by in muscle during exercise?

Isocitrate dehydrogenase plays a crucial role in the citric acid cycle as it catalyzes the conversion of isocitrate to alpha-ketoglutarate, which is a key step in energy production. During muscle exercise, the activity of this enzyme is significantly increased by elevated levels of calcium ions (Ca2+).

When muscles contract, they release calcium ions, which serve as an important signaling molecule. In the context of energy metabolism, calcium helps activate various enzymes involved in the citric acid cycle, including isocitrate dehydrogenase. This activation is essential because it enhances the rate of the citric acid cycle, facilitating increased production of NADH and ATP to meet the higher energy demands of the working muscles during exercise.

The other options—ATP, NADH, and glucose—do not contribute to the activation of isocitrate dehydrogenase in this particular scenario. High levels of ATP and NADH actually indicate sufficient energy availability, leading to feedback inhibition of the citric acid cycle rather than stimulation. Glucose, while an important fuel source for muscle activity, does not directly influence the activity of isocitrate dehydrogenase in response to calcium during exercise. Thus, the interaction of calcium