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J. Biol. Chem., Vol. 259, Issue 18, 11383-11390, 09, 1984
CL Shriner and DL Brautigan
Cytosolic protein phosphotyrosine (PPT) phosphatase was measured using a
new substrate, Tyr(32P)-labeled bovine serum albumin. Kidney was found as a
particularly rich tissue source of PPT-phosphatase activity, containing
twice as much as liver and over 10-fold more than brain, heart, lung, or
skeletal muscle. An affinity column of Zn2+- iminodiacetate agarose
adsorbed up to 60% of the PPT-phosphatase present in kidney extracts.
Subsequent chromatography on DEAE-Sepharose separated the phosphatase into
two peaks, labeled I and II, that had Mr = 34,000 and 37,000, respectively,
upon gel filtration with Sephadex G- 75 Superfine. Overall purification of
850- and 1100-fold was achieved with a net 4% yield. Both phosphatases
hydrolyzed p- nitrophenylphosphate as well as the protein substrate in the
presence of EDTA. Peak I phosphatase activity displayed a neutral pH
optimum, had an absolute requirement for sulfhydryl compounds, and was
sensitive to trypsin, whereas Peak II activity had an acidic pH optimum and
was active without mercaptans. The two proteins also gave different
fragmentation patterns by gel electrophoresis after digestion with S.
aureus V8 protease. The results show that multiple forms of PPT phosphatase
specifically interact with Zn2+ and provide a basis for further structural
and functional comparisons among different members of the phosphoprotein
phosphatase family.
Cytosolic protein phosphotyrosine phosphatases from rabbit kidney. Purification of two distinct enzymes that bind to Zn2+-iminodiacetate agarose
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E. Fischer, H Charbonneau, and N. Tonks Protein tyrosine phosphatases: a diverse family of intracellular and transmembrane enzymes Science, July 26, 1991; 253(5018): 401 - 406. [Abstract] [PDF] |
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