So which enzyme? Isocytrade dehydrogenase. isocitric dehydrogenase basically transforms isocitrate into alpha ketoglutrate. And when we have high levels of ATP, it blocks the activity of this enzyme and that leads to a build up of isocitrate in the matrix of the mitochondria. Now, isocitrate, if recalled back to the citric acid cycle, can be interconverted into citrate. So it basically converts back and forth.