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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
1
|
| pubmed:dateCreated |
1978-12-2
|
| pubmed:abstractText |
Phosphoprotein phosphatase which dephosphorylates 32P-labeled nucleolar protein substrates was found in nucleoli of Novikoff hepatoma ascites cells and normal rat liver. The activity was extracted in high yield from nucleoli with 0.01 M Bis/Tris (pH 7.0). Low ionic strength was also required for activity: the activity was only 50% of maximum in 0.075 M NaCl. Activity was affected differently by various divalent cations: MgCl2 had little effect: CaCl2, MnCl2 and CoCl2 above 4 mM inhibited the activity 30--60%; ZnCl2 above 2 mM completely destroyed the activity. EDTA had no effect, indicating that divalent cations are probably not required. The enzyme activity was enhanced 20% by 5--8 mM dithiothreitol and was inhibited 60% by 7--10 mM N-ethylmaleimide indicating a requirement for free sulfhydryl groups. The Km of the extracted enzyme for 32P-labeled nucleolar protein was 0.6 mg/ml. The phosphatase was capable of dephosporylating the major phosphorylated nucleolar proteins C23-24 and B23-24 and also histone H1. The enzyme was purified more than 200-fold on hydroxyapatite followed by DEAE-Sephadex, which resolved the activity into three major components. The activity of enzyme extracted from Novikoff hepatoma nucleoli was approximately 2.5 times greater than from normal liver nucleoli.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Sep
|
| pubmed:issn |
0006-3002
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
11
|
| pubmed:volume |
526
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
174-85
|
| pubmed:dateRevised |
2007-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:210825-Animals,
pubmed-meshheading:210825-Cations, Divalent,
pubmed-meshheading:210825-Cell Nucleolus,
pubmed-meshheading:210825-Chick Embryo,
pubmed-meshheading:210825-Kinetics,
pubmed-meshheading:210825-Liver,
pubmed-meshheading:210825-Liver Neoplasms, Experimental,
pubmed-meshheading:210825-Phosphoprotein Phosphatases,
pubmed-meshheading:210825-Rats,
pubmed-meshheading:210825-Substrate Specificity,
pubmed-meshheading:210825-Sulfhydryl Reagents
|
| pubmed:year |
1978
|
| pubmed:articleTitle |
Nucleolar phosphoprotein phosphatase from Novikoff hepatoma and rat liver: characterization and partial purification.
|
| pubmed:publicationType |
Journal Article
|