Final answer:
In a fasted state, pyruvate kinase is off. The enzyme's activity is regulated by factors like alanine supply and fructose-1,6-bisphosphate levels. ATP also plays a role in regulating the enzyme.
Step-by-step explanation:
In a fasted state, pyruvate kinase is off.
The enzyme's activity is regulated by several factors. When no more energy is needed and an adequate supply of the amino acid alanine is present, the enzyme is inhibited. Additionally, the enzyme's activity is increased when fructose-1,6-bisphosphate levels increase. The regulation of pyruvate kinase also involves phosphorylation and dephosphorylation reactions. ATP acts as a negative allosteric effector, further regulating the enzyme's activity.