Final answer:
Pyruvate kinase is inhibited by high levels of ATP, which acts as a negative allosteric regulator, and by ample alanine supply, signaling no further need for energy.
Step-by-step explanation:
Two factors that inhibit pyruvate kinase, an essential enzyme in glycolysis, are high levels of ATP and the presence of alanine. ATP acts as a negative allosteric regulator, meaning that it binds to the enzyme at a spot other than the active site, causing a change in the enzyme's conformation and reducing its activity. Similarly, when alanine is sufficiently available, it signals that the body does not require more energy, thereby inhibiting pyruvate kinase to prevent unnecessary production of ATP. Phosphorylation also regulates this enzyme; it becomes less active when phosphorylated by pyruvate kinase kinase, but dephosphorylation by a phosphatase can reactivate it.