PURIFICATION AND PROPERTIES OF A KINASE WHICH PHOSPHORYLATES AND INACTIVATES ACETYL-COA CARBOXYLASE

  • 1 January 1982
    • journal article
    • research article
    • Vol. 257  (4) , 1897-1901
Abstract
A protein kinase which phosphorylates and inactivates acetyl-CoA carboxylase was purified to apparent homogeneity from rat liver. The kinase was found to exist in 2 forms: bound to carboxylase in a complex or in a free form that is in different stages of aggregation over a wide range of MW. The purification of the kinase involved first partial purification of acetyl-CoA carboxylase through polyethylene glycol precipitation and DEAE-cellulose chromatography. The kinase was then separated from acetyl-CoA carboxylase by Sepharose 2B chromatography. The MW of the kinase subunit was 170,000 as determined by sodium dodecyl sulfate-gel electrophoresis. The incorporation of 1 mol of phosphate/mol of carboxylase subunit caused complete inactivation of the carboxylase. Acetyl-CoA carboxylase, inactivated by the kinase, can be dephosphorylated and reactivated when incubated with phosphorylase phosphatase. The Km values of the kinase for acetyl-CoA carboxylase and ATP are 90 nM and 20 .mu.M, respectively. The kinase was found to be cAMP-independent, but activated by CoA. The protein kinase can phosphorylate acetyl-CoA carboxylase, protamine, and histones, but could not act on hydroxymethylglutaryl-CoA reductase or phosphorylase b.

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