In the dehydration reaction of glycolysis
glyceraldehyde-3-phosphate is converted to 3-phosphoglyceric acid.
3-phosphoglyceric acid is converted to 2-phosphoglyceric acid.
2-phosphoglyceric acid is converted to phosphoenolpyruvic acid
phosphoenolpyruvic acid is converted to pyruvic acid.
Water is liberated during the conversion of 2-phosphoglyceric acid to phosphoenolpyruvic acid by the action of enolase enzyme.