Keto–enol tautomerism is important in several areas of biochemistry.
The high phosphate-transfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is "trapped" in the less thermodynamically favorable enol form, whereas after dephosphorylation it can assume the keto form.
The enzyme enolase catalyzes the dehydration of 2-phosphoglyceric acid to the enol phosphate ester.  Metabolism of PEP to pyruvic acid by pyruvate kinase (PK) generates adenosine triphosphate (ATP) via substrate-level phosphorylation.