Zhu Z, Ling S, Yang Q H, Li L
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.
Biol Chem. 2000 Dec;381(12):1195-202. doi: 10.1515/BC.2000.147.
The fructose-2,6-bisphosphatase domain of the bifunctional chicken liver enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase shares approximately 95% amino acid sequence homology with that of the rat enzyme. However, these two enzymes are significantly different in their phosphatase activities. In this report, we show that the COOH-terminal 25 amino acids of the two enzymes are responsible for the different enzymatic activities. Although these 25 amino acids are not required for the phosphatase activity, their removal diminishes the differences in the activities between the two enzymes. In addition, two chimeric molecules (one consisting of the catalytic core of the chicken bisphosphatase domain and the rat COOH-terminal 25 amino acids, and the other consisting of most of the intact chicken enzyme and the rat COOH-terminal 25 amino acids) showed the same kinetic properties as the rat enzyme. Furthermore, substitution of the residues Pro456Pro457Ala458 of the chicken enzyme with GluAlaGlu, the corresponding sequence in the rat liver enzyme, yields a chicken enzyme that behaves like the rat enzyme. These results demonstrate that the different bisphosphatase activities of the chicken and rat liver bifunctional enzymes can be attributed to the differences in their COOH-terminal amino acid sequences, particularly the three residues.
双功能鸡肝酶6-磷酸果糖-2-激酶/果糖-2,6-二磷酸酶的果糖-2,6-二磷酸酶结构域与大鼠酶的该结构域氨基酸序列同源性约为95%。然而，这两种酶的磷酸酶活性存在显著差异。在本报告中，我们表明这两种酶的COOH末端25个氨基酸决定了不同的酶活性。尽管这25个氨基酸并非磷酸酶活性所必需，但去除它们会减小两种酶活性之间的差异。此外，两个嵌合分子（一个由鸡双磷酸酶结构域的催化核心和大鼠COOH末端25个氨基酸组成，另一个由大部分完整的鸡酶和大鼠COOH末端25个氨基酸组成）表现出与大鼠酶相同的动力学特性。此外，将鸡酶的Pro456Pro457Ala458残基替换为大鼠肝酶中的相应序列GluAlaGlu，得到的鸡酶表现得与大鼠酶相似。这些结果表明，鸡和大鼠肝双功能酶不同的双磷酸酶活性可归因于它们COOH末端氨基酸序列的差异，特别是这三个残基。
