SUMMARY: Protein kinases I (PK I) and II (PK II) were purified 253- and 13.5-fold, respectively, from an extract of sonically disrupted cells of by ion-exchange chromatography on QAE-Sephadex, by histone affinity chromatography, and by HPLC-gel filtration chromatography. Both enzymes catalysed the phosphorylation of calf thymus histones, with a of 2.7 mg ml for PK I and 2.9 mg ml for PK II. Histone H was the best protein kinase substrate for both PK I and PK II. The pH optima were 6.8 and 7.0 for PK I and PK II respectively. The for ATP was 0.29 m for PK I and 0.33 m for PK II. PK II activity was stimulated by either cAMP or cGMP, whereas PK I was inhibited by both cyclic nucleotides. The activity of PK I was unaffected by addition of calmodulin, diacylglycerol and mixtures of Ca and acidic phospholipids, but these additions increased PK II activity threefold. The activity of PK II was stimulated by spermine and spermidine, but PK I was inhibited by these compounds. PK I and PK II were both strongly inhibited by heparin.


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