Hod Y, Utter M F, Hanson R W
J Biol Chem. 1982 Nov 25;257(22):13787-94.
Previous work from our laboratory (Watford, M., Hod, Y., Chiao, Y. B., Utter M. F., and Hanson R. W. (1981) J. Biol. Chem. 256, 10023-10027) indicated that in the chicken, hepatic phosphoenolpyruvate carboxykinase is in the mitochondria, whereas kidney contains both a mitochondrial and cytosolic form of the enzyme. In the present study the two forms of phosphoenolpyruvate carboxykinase were purified and shown to be distinct proteins which differ in size, charge, and immunochemical properties. Using a cell-free protein synthesis system, we demonstrate that the cytosolic isozyme is encoded only by kidney mRNA and that its translation form has similar properties to that of the mature protein. On the other hand, the mitochondrial enzyme is encoded by liver and kidney mRNA and synthesized as a protein about 2000 daltons larger than the mature form. The putative precursor of the mitochondrial phosphoenolpyruvate carboxykinase is processed to a mature size by isolated, respiring mitochondria. We further show that the mRNA species for the cytosolic and mitochondrial forms are separable and are about 3 and 4 kilobases, respectively. It is concluded that the two forms of phosphoenolpyruvate carboxykinase of the chicken are encoded by distinct mRNA species.
我们实验室之前的研究工作（沃特福德，M.，霍德，Y.，乔，Y.B.，厄特，M.F.，以及汉森，R.W.（1981年）《生物化学杂志》256卷，10023 - 10027页）表明，在鸡体内，肝脏中的磷酸烯醇式丙酮酸羧激酶存在于线粒体中，而肾脏中则同时含有该酶的线粒体形式和胞质形式。在本研究中，我们对磷酸烯醇式丙酮酸羧激酶的两种形式进行了纯化，并证明它们是不同的蛋白质，在大小、电荷和免疫化学性质上存在差异。利用无细胞蛋白质合成系统，我们证明胞质同工酶仅由肾脏mRNA编码，并且其翻译产物具有与成熟蛋白相似的性质。另一方面，线粒体酶由肝脏和肾脏的mRNA编码，合成的蛋白质比成熟形式大约大2000道尔顿。线粒体磷酸烯醇式丙酮酸羧激酶的假定前体可被分离的、进行呼吸作用的线粒体加工成成熟大小。我们还进一步表明，胞质和线粒体形式的mRNA种类是可分离的，分别约为3千碱基和4千碱基。结论是，鸡体内磷酸烯醇式丙酮酸羧激酶的两种形式由不同的mRNA种类编码。
