Tiganis T, House C M, Kemp B E
St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
Arch Biochem Biophys. 1996 Jan 15;325(2):289-94. doi: 10.1006/abbi.1996.0036.
The regulatory beta-subunit of the protein kinase CK2 modulates the salt optimum for alpha-subunit activity. In the presence of salt the beta-subunit is stimulatory while in the absence of salt it is inhibitory. In the presence of 150 mM NaCl CK2 has linear kinetics (Lineweaver-Burk) for the synthetic substrate RRRDDDSDDD with an apparent Km of 60 microM. In contrast, CK2 displayed biphasic kinetics for the peptide substrate when assayed in the absence of added NaCl. Biphasic kinetics were also obtained for other peptides but not for calsequestrin or casein. Recombinant alpha-subunit had strictly linear kinetics in the absence of added NaCl with an apparent Km of 104 microM. Preincubation of CK2 with ATP/Mg2+ or GTP/Mg2+, but not adenosine/Mg2+ or Mg2+ alone, resulted in kinetics that were near linear. This change in kinetics was dependent on enzyme conditions of low salt CK2 displays biphasic kinetics for peptide substrates, the biphasic kinetics require the presence of the beta-subunit, and ATP/Mg2+ binding reverses the effect.
蛋白激酶CK2的调节性β亚基可调节α亚基活性的最佳盐浓度。在有盐存在时，β亚基具有刺激作用，而在无盐时则具有抑制作用。在150 mM NaCl存在下，CK2对合成底物RRRDDDSDDD具有线性动力学（Lineweaver-Burk），表观Km为60 μM。相比之下，在不添加NaCl的情况下进行测定时，CK2对肽底物表现出双相动力学。其他肽也得到了双相动力学，但钙网蛋白或酪蛋白没有。重组α亚基在不添加NaCl的情况下具有严格的线性动力学，表观Km为104 μM。CK2与ATP/Mg2+或GTP/Mg2+预孵育，但不与腺苷/Mg2+或单独的Mg2+预孵育，会导致动力学接近线性。这种动力学变化取决于低盐的酶条件。CK2对肽底物表现出双相动力学，双相动力学需要β亚基的存在，并且ATP/Mg2+结合可逆转这种效应。
