page_title: Phosphoglycolate phosphatase
section_title: Mechanism
hierarchical_section_title: Phosphoglycolate phosphatase / Mechanism
caption_attribution_description: English: Reaction mechanism of phosphoglycolate phosphatase
context_page_description: Phosphoglycolate phosphatase, also commonly referred to as phosphoglycolate hydrolase, 2-phosphoglycolate phosphatase, P-glycolate phosphatase, and phosphoglycollate phosphatase, is an enzyme responsible for catalyzing the conversion of 2-phosphoglycolate into glycolate and phosphate. First studied and purified within plants, phosphoglycolate phosphatase plays a major role in photorespiratory 2-phosphoglycolate metabolism, an essential pathway for photosynthesis in plants. The occurrence of photorespiration in plants, due to the lack of substrate specificity of rubisco, leads to the formation of 2-phosphoglycolate and 3-phosphogylcerate. PGA is the normal product of carboxylation and will enter the Calvin cycle. Phosphoglycolate, which is a potent inhibitor of phosphofructokinase and triosephosphate isomerase, must be quickly metabolized and transformed into a useful substrate, and phosphoglycolate phosphatase catalyzes the first step in the regeneration of 3-phosphoglycerate from 2-phosphoglycolate at the expense of energy in the form of ATP.
  Since the discovery of its activity in plants, it has been purified within human cells and implicated in 2,3-DPG regulation.
context_section_description: This enzyme belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds.
  The hydrolysis of phosphoglycolate begins with the nucleophilic attack by an aspartate residue on the electrophilic phosphorus of the phosphoglycolate. The susceptibility of the bond between phosphate and glycolate is heightened by two key interactions. An interaction with the cofactor, Mg²⁺, helps polarize the phosphate-oxygen bond and therefore increases the electrophilicity of the phosphorus atom. The other interaction of the phosphate with serine and lysine residues further increases the electrophilicity of the phosphorus atom. In addition, the Mg²⁺ also orients the nucleophilic aspartate.
  The loss of the phosphate glycolate bond causes the nucleophilic aspartate to be phosphorylated, producing the enzyme intermediate, while glycolate is released from the active site. The interaction of the phosphorylated intermediate is stabilized by an interaction between the phosphate and a lysine residue. The Mg²⁺ located in the active site activates a water molecule to produce an hydroxide ion, which then hydrolyzes the phosphorylated aspartate and regenerates an active enzyme while releasing phosphate.
caption: Reaction mechanism of phosphoglycolate phosphatase:
       2-phosphoglycolate + H2O ⇌ glycolate + phosphate
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