| 1. |
- Dahlqvist-Edberg, Ulla, et al.
(författare)
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Purification of a Ca2+-activated protease from rat erythrocytes and its possible effect on pyruvate kinase in vivo
- 1981
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Ingår i: Biochimica et Biophysica Acta-Enzymology. - : Elsevier BV. - 0005-2744. ; 660:1, s. 96-101
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Tidskriftsartikel (refereegranskat)abstract
- A Ca2+-activated protease with [32P]phosphopyruvate kinase as substrate was purified to about 50% from rat erythrocytes. The purification involved chromatography on Sepharose/Sephadex gels, DEAE-cellulose and (NH4)2SO4 precipitation. The protease required 3.3 mM Ca2+ for full activity. When pyruvate kinase (ATP: pyruvate 2-O-phosphotransferase, EC 2.7.1.40) was purified from erythrocytes incubated with [32P]phosphate it contained 0.5 mol [32P]phosphate/mol enzyme subunit. When 3.3 mM Ca2+ were added at hemolysis this incorporation decreased. The possible importance of this Ca2+-activated protease for the regulation of pyruvate kinase in erythrocytes is discussed.
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| 2. |
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| 3. |
- Dahlqvist-Edberg, Ulla, et al.
(författare)
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The demonstration in rat liver cell sap of protein kinase and phosphoprotein phosphatase active on fructose-bisphosphatase
- 1982
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Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. - : Elsevier BV. - 0167-4838 .- 1879-2588. ; 706:2, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- A protein kinase active on fructose-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) was demonstrated in rat liver cell sap. The protein kinase activity was stimulated by cyclic AMP and coincided with the activity of cyclic AMP-dependent protein kinase type I. In addition, three different peaks of phosphoprotein phosphatase active on [32P] phosphofructose-bisphosphatase were found on chromatography of rat liver cell sap on a DEAE-cellulose column. These phosphatases needed divalent cations for full activity. 5'-AMP, a negative modulator of fructose-bisphosphatase, had no effect on the phosphorylation-de-phosphorylation reactions of the enzyme. ATP and Ca2+ did not influence the dephosphorylation reaction of fructose-bisphosphatase.
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| 4. |
- Ek, Pia, et al.
(författare)
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The kinetics of unphosphorylated, phosphorylated and proteolytically modified fructose bisphosphatase from rat liver
- 1981
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Ingår i: Biochimica et Biophysica Acta. - 0005-2744. ; 662:2, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorylation of fructose-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) by the catalytic subunit of cyclic AMP-dependent protein kinase from pig muscle decreased the K0.5 for fructose-bisphosphate from 21 to 11 microM. When the phosphorylated fructose-bisphosphatase was treated with trypsin the K0.5 increased to 22 microM. The K0.5 also increased when the phosphoenzyme was treated with a partially purified phosphatase from rat liver. There was no difference between the unphosphorylated and phosphorylated enzyme with respect to pH dependence, the pH optimum being about 7.0 for both. Limited treatment of fructose-bis-phosphatase with subtilisin, which cleaves the enzyme at its unphosphorylatable N-terminal part, increased the pH optimum more than limited treatment with trypsin, which releases the phosphorylated peptide at the C-terminal part of fructose-bisphosphatase. The phosphorylated site on the phosphorylated fructose-bisphosphatase was more easily split off by trypsin treatment than the corresponding unphosphorylated site. The results suggest in addition to the glucagon-induced phosphorylation of fructose-bisphosphatase described by Claus et al. [1] that the phosphorylation-dephosphorylation of fructose-bisphosphatase could be of importance for the hormonal regulation of the enzyme in vivo.
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| 5. |
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| 6. |
- Humble, Elisabet, et al.
(författare)
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Amino acid sequence at the phosphorylated site of rat liver fructose-1,6-diphosphatase and phosphorylation of a corresponding synthetic peptide
- 1979
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - 0006-291X .- 1090-2104. ; 90:3, s. 1064-1072
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Tidskriftsartikel (refereegranskat)abstract
- Rat liver fructose-1,6-diphosphatase was phosphorylated with (32P)ATP and the catalytic subunit of cyclic AMP-dependent protein kinase from pig muscle. After digestion with pepsin, α-chymotrypsin and subtilisin a peptide with the amino-terminal sequence Ser-Arg-Tyr-(32P)SerP-Leu-Pro-Leu-Pro was isolated. A synthetic unphosphorylated heptapeptide with the same amino acid sequence, ending with leucine, was phosphorylated with an apparent Km of 400 μM, while the apparent Km value for fructose-1,6-diphosphatase was 30 μM (subunit concentration). The Vmax value was 20 times higher for the peptide than for the enzyme.
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