A novel 35 kDa frog liver acid metallophosphatase

Szalewicz, Agata; Radomska, Barbara; Strzelczyk, Barbara; Kubicz, Aleksandra

doi:10.1016/s0167-4838(99)00029-1

Cited by 2 publications

(4 citation statements)

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“…On the other hand, the presence of a single tetrahedral oxyanion binding site differentiates the frog enzyme from the mammalian ones for which the noncompetitive or mixed character of inhibition suggest a presence of multiple binding sites for these inhibitors (Vincent et al, 1991;Crans et al, 1992;Vincent et al, 1992). In our earlier paper (Szalewicz et al, 1999a) we have presented the data indicating that the frog liver LMW AcPase is a novel metallophosphatase different from those belonging to the class of mammalian TRAPs. The new data presented in this paper allow us to extend our comparison.…”

Section: Discussionmentioning

confidence: 96%

“…The LMW acid phosphatase from frog (Rana esculenta) livers was extracted with 0.1 M Na/acetate buffer, pH 5.0, containing 0.1 mM PMSF and 1 mM DTT, and purified subsequently by ammonium sulfate fractionation, Con A-affinity chromatography, Bio-Gel P-200 filtration and ion exchange chromatography on Mono S column as described earlier (Jañska et al, 1989;Szalewicz et al, 1999a).…”

Section: Enzyme Purificationmentioning

confidence: 99%

“…The low molecular mass acid phosphatase (LMW AcPase, M 35 kDa) from the frog liver described by our group has been shown to be a novel metallophosphatase activated by reducing agents and displaying tartrate-resistance (Jañska et al, 1989: Szalewicz et al, 1999a. It differs from the mammalian, tartrate-resistant purple acid phosphatases by the involvement of different metal ions in the catalytic process and in the way of iron coordination.…”

mentioning

confidence: 99%

“…It differs from the mammalian, tartrate-resistant purple acid phosphatases by the involvement of different metal ions in the catalytic process and in the way of iron coordination. There is also no immunological relationship between the protein moieties of these enzymes (Szalewicz et al, 1999a). We previously showed that the frog LMW AcPase is able to hydrolyze phosphotyrosine at acidic pH and its optimum for this substrate is shifted towards neutral pH in the presence of some divalent metal cations (Szalewicz et al, 1999b).…”

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confidence: 99%

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The 35 kDa acid metallophosphatase of the frog Rana esculenta liver: studies on its cellular localization and protein phosphatase activity.

Szalewicz¹,

Strzelczyk²,

Sopel³

et al. 2003

Acta Biochim Pol

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The cellular localization of the 35 kDa, low molecular mass acid metallophosphatase (LMW AcPase) from the frog (Rana esculenta) liver and its activity towards P-Ser and P-Tyr phosphorylated peptides were studied. This enzyme was localized to the cytoplasm of hepatocytes but did not appear in other cells of liver tissue (endothelium, macrophages, blood cells). This LMW AcPase does not display activity towards (32)P-phosphorylase a under conditions standard for the enzymes of PPP family. Proteins containing P-Ser: rabbit (32)P-phosphorylasea and phosvitin are hydrolysed only at acidic pH and are poor substrates for this enzyme. The frog AcPase is not inhibited by okadaic acid and F(-) ions, the Ser/Thr protein phosphatase inhibitors. Moreover, the frog enzyme does not cross-react with specific antisera directed against N-terminal fragment of human PP2A and C-terminal conserved fragment of the eukaryotic PP2A catalytic subunits. These results exclude LMW AcPase from belonging to Ser/Thr protein phosphatases: PP1c or PP2Ac. In addition to P-Tyr, this enzyme hydrolyses efficiently at acidic pH P-Tyr phosphorylated peptides (hirudin and gastrin fragments). K(m) value for the hirudin fragment (7.55 +/- 1.59 x 10(-6) M) is 2-3 orders of magnitude lower in comparison with other substrates tested. The enzyme is inhibited competitively by typical inhibitors of protein tyrosine phosphatases (PTPases): sodium orthovanadate, molybdate and tungstate. These results may suggest that the LMW AcPase of frog liver can act as PTPase in vivo. A different cellular localization and different response to inhibition by tetrahedral oxyanions (molybdate, vanadate and tungstate) provide further evidence that LMW AcPase of frog liver is distinct from the mammalian tartrate-resistant acid phosphatases.

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