Phosphoenolpyruvate (PEP) is a key intermediate in the metabolic pathway of glycolysis, which is the process that breaks down glucose to produce energy. It is formed from 2-phosphoglycerate through the action of the enzyme enolase. PEP plays a crucial role in cellular respiration, as it is converted into pyruvate by the enzyme pyruvate kinase, releasing energy in the form of ATP. In addition to its role in glycolysis, PEP is also involved in the gluconeogenesis pathway, where it is synthesized from pyruvate to help produce glucose. This makes PEP an important molecule in maintaining energy balance and supporting various metabolic functions in living organisms.