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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 Legionella micdadei 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 K m of 2·7 mg ml−1 for PK I and 2·9 mg ml−1 for PK II. Histone H2b 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 K m for ATP was 0·29 mm for PK I and 0·33 mm 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 Ca2+ 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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