Fill un the blanks In enolase, the reaction mechanism uses lysine at position 345 as a base to remove a proton from 2-phosphoglycerate as the first step. However, this results in an increased negative charge on the carboxylate group of the resulting carbanion intermediate. There are Mg2 ions near the carboxylate part that function to the stability of the carbanion intermediate prior to glutamic acid at position 211, donating a proton to the intermediate in order to form the final product, phosphoenolpyruvate.