Two phosphatases for 6-phospholysine and 3-phosphohistidine from rat brain.

6-Phospholysine phosphatase (30 kDa) and 3-phosphohistidine/6-phospholysine phosphatase (150 kDa) were purified partially from rat brain cytosol. The former hydrolyzed 6-phospholysine to inorganic phosphate and lysine, and the Km value was 0.83 mM. The latter hydrolyzed 6-phospholysine or 3-phosphohistidine to inorganic phosphate and lysine or histidine, and the Km values were 0.78 and 0.37 mM for 6-phospholysine and 3-phosphohistidine, respectively. Moreover, the latter enzyme preparation dephosphorylated AMP, GMP, and p-nitrophenyl phosphate. Substrate specificities of both enzymes were distinct from those of N omega-phosphoarginine phosphatase (Kuba, M., Ohmori, H., and Kumon, A. (1992) Eur. J. Biochem. 208, 747-752) and phosphoamidase (EC 3.9.1.1), indicating that there are phosphatases corresponding to N-phosphorylated basic amino acids. The possibility that these enzymes work in vivo as protein phosphatases to regulate the level of N-phosphorylated proteins is discussed.