Multiple forms of phosphatase from human brain: isolation and partial characterization of affi-gel blue nonbinding phosphatase activities.
Phosphatases extracted from a human brain were resolved into two main groups, namely affi-gel blue-binding phosphatases and affi-gel blue-nonbinding phosphatases. Affi-gel blue binding phosphatases were further separated into four different phosphatase activities, designated P1-P4, and described previously. In the present study we describe the affi-gel blue-nonbinding phosphatases which were separated into seven different phosphatase activities, designated P5-P11 by poly-(L-lysine)-agarose and aminohexyl Sepharose 4B chromatographies. These seven phosphatase activities were active toward nonprotein phosphoester. P7-P11 and to some extent P5 could also dephosphorylate a phosphoprotein. They displayed different enzyme kinetics. On the basis of activity peak, the apparent molecular mass as estimated by Sephadex G-200 column chromatography for P5 was 49 kDa; P6, 32 kDa; P7, 150 kDa; P8, 250 kDa; P9, 165 kDa; P10, 90 kDa and P11, 165 kDa. Immunoblot analysis indicated that P8-P11 may belong to PP2B family, whereas P7 may associate with PP2A. The phosphatases P7-P11 were found to be effective in the dephosphorylation of Alzheimer's disease abnormally hyperphosphorylated tau. The resulting dephosphorylated tau regained its activity in promoting the microtubule assembly, suggesting that P7-P11 might regulate the phosphorylation of tau protein in the brain.