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Membrane-associated pyruvate kinase in developing guinea-pig liver.
The Biochemical Journal
|April 1, 1986
Summary
Pyruvate kinase activity in developing guinea-pig liver microsomes is substantial and distinct from cytosolic forms. These hydrophobic membrane-bound enzymes may be precursors or part of a functional glycolytic pathway.
Area of Science:
- Biochemistry
- Cell Biology
- Developmental Biology
Background:
- Pyruvate kinase is a key glycolytic enzyme.
- Its distribution and forms in developing liver microsomes are not well understood.
Purpose of the Study:
- To investigate the presence, characteristics, and potential role of pyruvate kinase in developing guinea-pig liver microsomes.
Main Methods:
- Enzyme activity assays
- Sucrose and detergent extraction
- Triton X-100 inactivation studies
- DEAE-cellulose chromatography
- Isoelectric focusing
- Kinetic analysis
Main Results:
- A significant portion of pyruvate kinase activity was associated with liver microsomes.
- Microsomal pyruvate kinase required detergent for release and showed distinct properties from cytosolic forms.
- The microsomal enzyme was less stable and susceptible to Triton X-100 inactivation.
- Isoelectric focusing revealed at least four distinct microsomal pyruvate kinase forms, differing from cytosolic isoenzymes.
- Kinetic properties suggested these microsomal forms might be counterparts to cytosolic isoenzymes.
Conclusions:
- Developing liver microsomes contain a unique, hydrophobic pyruvate kinase fraction.
- These microsomal forms may represent precursors to cytosolic pyruvate kinase isoenzymes.
- Microsomal pyruvate kinase could play a role in a functional glycolytic pathway within the microsomes.