Dobrowolska G, Meggio F, Marchiori F, Pinna L A
Dipartimento di Chimica Biologica, Università di Padova, Italy.
Biochim Biophys Acta. 1989 Feb 9;1010(2):274-7. doi: 10.1016/0167-4889(89)90173-0.
The site specificity of maize seedling casein kinase-IIB, a type-2 casein kinase exhibiting an unusually low Mr, has been studied with the aid of model acidic peptide substrates for rat liver casein kinase-2. Like the animal enzyme, casein kinase-IIB also readily phosphorylates peptides SEEEEE, SEAEEE and SEEEAE, but not SEEAEE. Maize seedling casein kinase-IIB, however, is almost inactive toward peptides SAEEEE, SAEEEEE and SAAEEEEE which are good substrates for liver casein kinase-2. This indicates that casein kinase-IIB requires acidic residues not only at position +3, similar to rat liver casein kinase-2, but also at position +1, where the animal enzyme tolerates a neutral residue. This and other differences outlined in this report support the view that protein kinases of the same type from different sources may have significant differences in their substrate specificity.
借助大鼠肝脏酪蛋白激酶 -2 的模型酸性肽底物，对玉米幼苗酪蛋白激酶 -IIB（一种分子量异常低的 2 型酪蛋白激酶）的位点特异性进行了研究。与动物酶一样，酪蛋白激酶 -IIB 也能轻易地使肽 SEEEEE、SEAEEE 和 SEEEAE 磷酸化，但不能使 SEEAEE 磷酸化。然而，玉米幼苗酪蛋白激酶 -IIB 对肽 SAEEEE、SAEEEEE 和 SAAEEEEE 几乎没有活性，而这些肽是肝脏酪蛋白激酶 -2 的良好底物。这表明酪蛋白激酶 -IIB 不仅像大鼠肝脏酪蛋白激酶 -2 一样在 +3 位需要酸性残基，而且在 +1 位也需要酸性残基，而动物酶在该位置可耐受中性残基。本报告中概述的这一差异及其他差异支持了这样一种观点，即来自不同来源的同一类型蛋白激酶在底物特异性方面可能存在显著差异。
