Which enzymes are affected by elevated ATP levels?

Elevated ATP levels signal the energy status of the cell, which leads to the regulation of various metabolic pathways, including the Citric Acid Cycle (CAC), often referred to as the Krebs cycle. The enzymes that are particularly sensitive to high ATP concentrations include citrate synthase, isocitrate dehydrogenase, and alpha-ketoglutarate dehydrogenase.

Citrate synthase catalyzes the first step of the cycle, combining acetyl-CoA and oxaloacetate to form citrate. When ATP levels are high, indicating sufficient energy supply, the activity of citrate synthase is inhibited, preventing the cycle from continuing when energy is not needed.

Isocitrate dehydrogenase is an important regulatory enzyme in the cycle, converting isocitrate to alpha-ketoglutarate. This enzyme is allosterically inhibited by ATP as well, which helps to control the flow through the cycle based on the cell's energy demand.

Alpha-ketoglutarate dehydrogenase also plays a similar role, facilitating the conversion of alpha-ketoglutarate to succinyl-CoA. It is sensitive to high energy levels, such as ATP, and is regulated accordingly to reduce flux through the cycle when ATP is abundant