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Dephosphorylation of pig heart pyruvate dehydrogenase phosphate complexes by pig heart pyruvate dehydrogenase phosphate phosphatase.
- Source :
-
The Biochemical journal [Biochem J] 1981 Apr 01; Vol. 195 (1), pp. 51-9. - Publication Year :
- 1981
-
Abstract
- 1. Pig heart pyruvate dehydrogenase phosphate complex in which all three sites of phosphorylation were completely phosphorylated was re-activated at a slower rate by phosphatase than complex predominantly phosphorylated in site 1. The ratio of initial rates of re-activation was approx. 1:5 with a comparatively crude preparation of phosphatase and with phosphatase purified by gel filtration and ion-exchange chromatography. 2. The ratio of apparent first-order rate constants during dephosphorylation of fully phosphorylated complex averaged 1/3.8/1.3 for site 1/site 2/site 3. Only site-1 dephosphorylation was linearly correlated with re-activation of the complex throughout dephosphorylation. Dephosphorylation of site 3 was linearly correlated with re-activation after an initial burst of dephosphorylation. 3. Because dephosphorylation of site 1 was always associated with dephosphorylation of site 2, it is concluded that dephosphorylation cannot be purely random. 4. The ratio of apparent first-order rate constants for dephosphorylation of site 1 (partially/fully phosphorylated complexes) averaged 1.72. This ratio is smaller than the ratio of approx. 5 for the initial rates of re-activation. Possible mechanisms involved in the diminished rate of re-activation of fully phosphorylated complex are discussed.
Details
- Language :
- English
- ISSN :
- 0264-6021
- Volume :
- 195
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- The Biochemical journal
- Publication Type :
- Academic Journal
- Accession number :
- 6272748
- Full Text :
- https://doi.org/10.1042/bj1950051