title: Direct metal analyses of Mn2+-dependent and -independent protein phosphatase 2A from human erythrocytes detect zinc and iron only in the Mn2+-independent one.
abstract: A Mn2+-dependent protein phosphatase 2A which is composed of a 34 kDa catalytic C' subunit and a 63 kDa regulatory A' subunit, was purified from human erythrocyte cytosol. C' and A' produced V8- and papain-peptide maps identical to those of the 34 kDa catalytic C and the 63 kDa regulatory A subunits of the Mn2+-independent conventional protein phosphatase in human erythrocyte cytosol, respectively. Reconstitution of C'A and CA' revealed that the metal dependency resided in C' and not in A'. In CA, 0.87 +/- 0.12 mol zinc and 0.35 +/- 0.18 mol iron per mol enzyme were detected by atomic absorption spectrophotometry, but manganese, magnesium and cobalt were not detected. None of these metals was detected in C'A'. Pre-incubation of C' with ZnCl2 and FeCl2, but not FeCl3, synergistically stimulated the Mn2+-independent protein phosphatase activity. The protein phosphatase activity of C was unaffected by the same zinc and/or iron treatment. These results suggest that C is a Zn2+- and Fe2+-metalloenzyme and that C' is the apoenzyme.
authors.affiliation: Department of Biochemistry, Hiroshima University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nishito
authors.forename: H
authors.initials: H
authors.lastname: Usui
authors.forename: K
authors.initials: K
authors.lastname: Shinzawa-Itoh
authors.forename: R
authors.initials: R
authors.lastname: Inoue
authors.forename: O
authors.initials: O
authors.lastname: Tanabe
authors.forename: T
authors.initials: T
authors.lastname: Nagase
authors.forename: T
authors.initials: T
authors.lastname: Murakami
authors.forename: M
authors.initials: M
authors.lastname: Takeda
mesh_terms: D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000032:analysis*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology*; D008667:Metalloproteins / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000187:drug effects; D054648:Protein Phosphatase 2; D015032:Zinc / Q000032:analysis*
chemical_list: D001051:Apoenzymes; D020035:Holoenzymes; D008667:Metalloproteins; D008345:Manganese; D007501:Iron; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D008274:Magnesium; D015032:Zinc