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  • Title: Purification and properies of cAMP dependent and independent histone kinases from human leukocytes.
    Author: Juhl H, Esmann V.
    Journal: Mol Cell Biochem; 1979 Jul 15; 26(1):3-18. PubMed ID: 226866.
    Abstract:
    Histone kinase activity was purified from human polymorphonuclear leukocytes by ammonium sulphate precipitation of a 180 000 x g supernatant, followed by DEAE-cellulose chromatography and gelfiltration. On DEAE-cellulose cAMP dependent kinase activity eluted in two peaks, I and III, at 1.2 mmho and 6.5 mmho, respectively. Catalytic subunit (C) from both peaks had Mr 33 000, 3.0S. Regulatory subunit (R) from peak I and III both had Mr 33 000 upon gelfiltration, but sedimented at 2.8--3.0S and 3.0--3.2S, respectively. R2 and R4 subunits were identified. The R-C dimer from peak I and III sedimented at 4.8S and (4.8)--5.1S, respectively. The holoenzyme from peak I had Mr 165 000, 6.7S, which suggest a R2C2 structure, while that of peak III sedimented at 6.7S, but eluted at Mr 330 000 (2R2C2) by gelfiltration. The Kmapp for peak I and III enzymes were, respectively: histone IIA 0.5 mg/ml (both forms), ATP 18 microM and 23 microM, and cAMP 5 X 10(-8) M and 6.3 x 10(-8) M. Both enzymes had pH optimum 6.7--6.9 and were equally sensitive to Ca2+, temperature and protein kinase inhibitor. The substrate specificity was histone VS greater than histone IIA = histone VIS greater than casein greater than phosvitin. Peak I enzyme, but not peak III enzyme, was dissociated by histone and high ionic strength and reassociation of R and C subunits were facilitated by ATP-Mg. It is concluded that peak I and III enzymes represent type I and II cAMP dependent protein kinases, respectively. Type I comprises 20--30% of cAMP dependent protein kinase activity and is absent from the 180 000 x g supernatant of gently disrupted cells. Purified catalytic subunit had Kmapp (ATP) 20 microM with rabbit muscle glycogen synthease I as substrates. Synthase I from rabbit muscle and human leukocytes were phosphorylated by catalytic subunit to synthase D (ratio of independence less than 0.07). cAMP independent histone kinase activity eluted in one peak (Peak II) at3 mmho. The enzymatic activity sedimented at 3.4S and eluted from gelfiltration with Mr 78 000. Kmapp for ATP was 78 microM and for histone IIA 0.5 mg/ml. The enzyme was sensitive to temperature, but less sensitive than cAMP dependent protein kinase to Ca2+, and insensitive to protein kinase inhibitor. The substrate specificity was histone IIA greater than histone VS = histone VIS, while casein and phosvitin were poor substrates. Glycogen synthase I was not phosphorylated. The cAMP independent histone kinase activity comprised 15% of the total histone kinase activity in a crude homogenate of leukocytes. Its physiological substrate is unknown.
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