Endogenous basic protein phosphatases in the brain myelin.
Direct treatment of brain myelin with freezing/thawing in 0.2 M 2-mercaptoethanol stimulated the endogenous myelin phosphatase activity manyfold when 32P-labeled phosphorylase a was used as a substrate, a result indicating that an endogenous myelin phosphatase is a latent protein phosphatase. When myelin was treated with Triton X-100, this endogenous latent phosphatase activity was further stimulated 2.5-fold. Diethylaminoethyl-cellulose and Sephadex G-200 chromatography of solubilized myelin revealed a pronounced peak of protein phosphatase activity stimulated by freezing/thawing in 0.2 M 2-mercaptoethanol and with a molecular weight of 350,000, which is characteristic of latent phosphatase 2, as previously reported. Moreover, endogenous phosphorylation of myelin basic protein (MBP) in brain myelin was completely reversed by a homogeneous preparation of exogenous latent phosphatase 2. By contrast, under the same conditions, endogenous phosphorylation of brain myelin was entirely unaffected by ATP X Mg-dependent phosphatase and latent phosphatase 1, although both enzymes are potent MBP phosphatases. Together, these findings clearly indicate that a high-molecular-weight latent phosphatase, termed latent phosphatase 2, is the most predominant phosphatase responsible for dephosphorylation of brain myelin.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002850:Chromatography, Gel; D005615:Freezing; D008623:Mercaptoethanol / Q000494:pharmacology; D008970:Molecular Weight; D004676:Myelin Basic Protein / Q000378:metabolism; D009186:Myelin Sheath / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D013552:Swine
D004676:Myelin Basic Protein; D008623:Mercaptoethanol; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2