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Dissociation of phosphohistone phosphatases from canine heart
Insights
Canine heart phosphohistone phosphatase exists in multiple forms. Ethanol treatment reveals two basic constituents, phosphatase U and catalytic subunits (phosphatase S), suggesting a complex enzymatic structure.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Phosphohistone phosphatase (EC 3.1.3.16) plays a role in cellular regulation.
- Canine heart phosphohistone phosphatase exhibits multiple molecular forms.
Purpose of the Study:
- To characterize the molecular forms of canine heart phosphohistone phosphatase.
- To investigate the relationship between different molecular forms.
Main Methods:
- DEAE-cellulose chromatography was used to separate enzyme forms.
- Ethanol treatment was employed to dissociate enzyme subunits.
- Enzyme activity assays were performed under various conditions (ATP, Mn2+).
Main Results:
- Four molecular forms (A, B, C, U) were identified with distinct molecular weights.
- ATP differentially affected phosphatases A and B, while phosphatase U required Mn2+.
- Ethanol dissociation yielded a common catalytic subunit (phosphatase S) with increased activity.
Conclusions:
- Canine heart phosphohistone phosphatase exists as multiple forms.
- Phosphatase S represents a catalytic subunit common to forms A, B, and C.
- Phosphatase U and S may be the fundamental constituents of canine heart phosphohistone phosphatase.
Abstract:
Phosphohistone phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) of canine heart extract has been separated by DEAE-cellulose chromatography into 4 molecular forms, namely phosphatases A (Mr = 156 000), B (Mr = 161 000), C (Mr = 95 600) and U (Mr = 61 000). ATP inhibited phosphatase A, stimulated phosphatase B and did not significantly affect phosphatase C activity. Phosphatase U requires Mn2+ for activity, under which condition ATP is inhibitory. Phosphatases A, B and C, but not phosphatase U, were dissociated by ethanol into catalytic subunits that were inhibited by ATP, insensitive to Mn2+, and had a common molecular weight of 34 800 (phosphatase S). The dissociation was accompanied by an increase of enzymic activity. Chromatography of the ethanol-treated 55% (NH4)2SO4 fraction of canine heart extract on DEAE-cellulose demonstrated that the multiple forms of phosphohistone phosphatase could be reduced to two forms: phosphatase U and phosphatase S, which may represent two basic constituents of the multiple forms of phosphohistone phosphatase in canine heart.