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Cyclic AMP-independent casein/glycogen synthase kinases from pig polymorphonuclear leucocytes.
The Biochemical Journal
|March 1, 1981
Summary
Two cyclic AMP-independent casein/glycogen synthase kinases were purified from pig polymorphonuclear leucocytes. These enzymes exhibit distinct molecular weights, substrate affinities, and responses to KCl, impacting glycogen synthase phosphorylation differently.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Casein and glycogen synthase kinases play crucial roles in cellular regulation.
- Understanding these enzymes is vital for deciphering metabolic pathways.
Purpose of the Study:
- To purify and characterize cyclic AMP-independent casein/glycogen synthase kinases from pig polymorphonuclear leucocytes.
- To elucidate the distinct properties and functions of these purified kinases.
Main Methods:
- Purification using phosphocellulose chromatography, affinity chromatography (casein-Sepharose 4B), and gel filtration (Bio-Gel A-1.5m).
- Characterization of enzyme kinetics, molecular weight, substrate specificity, and response to various effectors (KCl, Mg2+).
Main Results:
- Two distinct kinases, casein kinase 1 (38 kDa) and casein kinase 2 (185 kDa), were purified.
- Kinetic parameters (Km for casein, Ka for Mg2+) and responses to KCl differed significantly between the two kinases.
- Both kinases phosphorylated rabbit muscle glycogen synthase I, but with different efficiencies and effects on its glucose 6-phosphate independence.
Conclusions:
- The purified kinases are distinct entities with unique biochemical properties.
- These enzymes exhibit differential regulation of glycogen synthase activity, suggesting diverse roles in cellular metabolism.
- Their activity is independent of cyclic AMP, Ca2+, and calmodulin.