Phosphoglycolate phosphatase from human red blood cells

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Phosphoglycolate phosphatase has been partially purified from human red blood cells. The enzyme requires Cl − and Mg 2+ for activity. Other anions, such as HCO 3 −, cacodylate, and F −, do not enhance the rate of the reaction whereas Br − and I − are both effective at even lower concentrations than Cl −. K a values are: Cl −, 35 m m; Br −, 7 m m; I −, 1 m m. All give the same maximal velocity. Higher levels of Cl − are inhibitory, with 30% inhibition at 0.2 m KCl and no activity observed with 0.4 m KCl. EDTA at 0.1 m m inhibits almost completely. The inhibition by EDTA can be overcome by Mg 2+. Glycerate-2- P, glycerate-3- P, and glycerate-2,3- P 2 are not hydrolyzed. The enzyme can hydrolyze ethyl- P with the same K m and maximal velocity as P-glycolate. n-Propyl- P and i-propyl- P are hydrolyzed more slowly. There is no inhibition by glycerate-2- P. The enzyme has a constant maximal velocity over the pH range from 5.5 to 9. The K m of P-glycolate is 1.5–2 m m from pH 5.5 to 7.5 and it increases at higher pH. The substrate is P-glycolate itself and the complex with Mg 2+ is inhibitory. The phosphatase is inhibited by low levels of iodoacetate and p-hydroxymercuribenzoate. Phosphoglycolate phosphatase may have a role in the regulation of the 2,3-bisphosphoglycerate level in the human red cell.