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Two splenic soluble tyrosine kinases from the rat
1Department of Biochemistry, Osaka City University Medical School, Japan.
Archives of Biochemistry and Biophysics
|July 1, 1990
Summary
Researchers purified two tyrosine kinases (TKI and TKI-II) from rat spleen cytoplasm. These enzymes autophosphorylate tyrosine residues and exhibit distinct kinetic properties, suggesting unique biological roles.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Tyrosine kinases play crucial roles in cellular signaling pathways.
- Understanding the specific properties of different tyrosine kinases is essential for elucidating their functions.
Purpose of the Study:
- To isolate and characterize tyrosine kinases involved in angiotensin signaling from rat spleen.
- To determine the biochemical properties and potential biological significance of purified tyrosine kinases.
Main Methods:
- Cytoplasmic fraction of rat spleen was prepared and subjected to ultracentrifugation.
- Tyrosine kinases were purified using column chromatography.
- Enzyme kinetics, molecular weight determination (gel filtration, SDS-PAGE), and autophosphorylation assays were performed.
Main Results:
- Two distinct tyrosine kinases, TKI and TKI-II, were purified from the 100,000g supernatant.
- Molecular weights were estimated to be approximately 38-42 kDa for TKI and 30-36 kDa for TKI-II.
- Both kinases demonstrated tyrosine autophosphorylation activity and exhibited different Km values for angiotensin II and ATP, with similar dependencies on temperature and divalent metal ions.
Conclusions:
- Rat spleen cytoplasm contains at least two distinct tyrosine kinases (TKI and TKI-II) capable of angiotensin II phosphorylation.
- The distinct kinetic parameters suggest specialized roles for these enzymes in cellular regulation.
- The identified kinases are likely genuine enzymes, not artifacts of proteolysis.