Direct metal analyses of Mn2+-dependent and -independent protein phosphatase 2A from human erythrocytes detect zinc and iron only in the Mn2+-independent one.
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.
Nishito
Y
Y
Department of Biochemistry, Hiroshima University School of Medicine, Japan.
Usui
H
H
Shinzawa-Itoh
K
K
Inoue
R
R
Tanabe
O
O
Nagase
T
T
Murakami
T
T
Takeda
M
M
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*
D001051:Apoenzymes; D020035:Holoenzymes; D008667:Metalloproteins; D008345:Manganese; D007501:Iron; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D008274:Magnesium; D015032:Zinc