Phosphate Transfer between 2,3‐Bisphosphoglycerate and Monophosphoglycerate Catalyzed by Bisphosphoglycerate Phosphatase

1 2,3‐Bisphosphoglycerate phosphatase from human erythrocytes was extensively purified with the use of various chromatographic procedures and electrofocusing. All detectable phosphoglyceromutase activity was removed as tested with an optical assay at pH 7.6. 2 At the pH optimum of the phosphatase reaction (pH 6.5) the enzyme transfers phosphate groups from 2,3‐bisphosphoglycerate to monophosphoglycerates (3‐phosphoglycerate or 2‐phosphoglycerate). The transfer is more than hundred times faster than the hydrolyzing activity. 3 Chloride and 2‐phosphoglycolate stimulate the hydrolyzing but not the transferring activity. 4 Data from seven experiments with differently labelled phosphoglycerates were analyzed in terms of rate constants defined by a mathematical model for the different transfer reactions.With the direction of phosphate transfer expressed from 2,3‐bisphosphoglycerate to mono‐phosphoglycerate the constants were estimated to have the following values (ml · min −1 ·μmol −1 ): C‐3 → C‐2 0.006 ± 0.001, C‐2 → C‐2 0.024 ± 0.003, C‐3 → C‐3 0.009 ± 0.006 and C‐2 → C‐3 0.034 ± 0.008. The values indicate that the velocity of the transfer from C‐2 in 2,3‐bisphosphoglyerate to the vacant carbon atom in 2‐phosphoglycerate is about the same or possibly somewhat higher than the velocity of the transfer to 3‐phosphoglycerate. The transfer velocity from 2,3‐[3‐ 32 P]bisphosphoglycerate to 3‐phosphoglycerate is much lower. Due to the experimental conditions the results do not allow determination of the velocity of the transfer from C‐3 to 2‐phosphoglycerate with any high degree of precision. The C‐3 to C‐2 transfer however, is slower than the transfer from C‐2 in 2,3‐bisphosphoglycerate.