Phosphotransferase properties of human erythrocyte phosphoglycolate phosphatase

1. Human erythrocyte phosphoglycolate phosphatase (PGP) (EC 3.1.3.18) shows transferase properties. Using p-nitrophenylphosphate (p-NPP) as substrate, methanol, at a concentration of 4.9 M, was the most efficient phosphate acceptor tested (60% phosphate transfer). 2. The branched alcohols i-propanol and i-butanol accept the phosphate better than the unbranched compounds. The acceptor potency is methanol greater than ethanol greater than i-propanol greater than n-propanol greater than i-butanol greater than n-butanol. 3. The relative transferase activity could be demonstrated to be independent of substrate concentration, pH, and the inhibitory effect of NaF at 2 and 4 mM. 4. PGP shows no transferase activity towards glucose and fructose, and is even inhibited by 250 mM of lactose and lactic acid to 67 and 55%, respectively. 5. Using p-nitrophenyl-[32P]-phosphate (p-NP[32P]P), the direct transfer of phosphate from donor to acceptor could be demonstrated.