Malherbe P, Alberati-Giani D, Köhler C, Cesura A M
Pharma Division, F. Hoffmann-La Roche Ltd., Basel, Switzerland.
FEBS Lett. 1995 Jun 26;367(2):141-4. doi: 10.1016/0014-5793(95)00546-l.
A soluble aminotransferase with kynurenine aminotransferase (KAT) activity has been recently isolated from rat brain. This enzyme corresponds to a cytosolic form of glutamine transaminase K (GTK). In addition to the cytosolic enzyme, a mitochondrial-associated form of this KAT/GTK also exists. In the present work we have isolated a rat brain cDNA clone encoding a KAT/GTK enzyme identical to the soluble form but carrying an additional stretch of 32 amino acids at its NH2-terminus. Several structural features of this sequence resemble those of leader peptides for mitochondrial import. Evidence that the isolated cDNA encoded for mitochondrial KAT/GTK was obtained after transfection of HEK-293 cells with the cDNA coding for this new KAT/GTK isoenzyme. In fact, a significant enrichment of both KAT and GTK enzymatic activities was found in the crude mitochondrial fraction of the transfected cells.
最近从大鼠脑中分离出一种具有犬尿氨酸转氨酶（KAT）活性的可溶性转氨酶。这种酶相当于谷氨酰胺转氨酶K（GTK）的胞质形式。除了胞质酶外，还存在这种KAT/GTK的线粒体相关形式。在本研究中，我们分离出一个大鼠脑cDNA克隆，其编码的KAT/GTK酶与可溶性形式相同，但在其NH2末端带有一段额外的32个氨基酸序列。该序列的几个结构特征类似于线粒体导入前导肽的特征。在用编码这种新的KAT/GTK同工酶的cDNA转染HEK-293细胞后，获得了分离的cDNA编码线粒体KAT/GTK的证据。事实上，在转染细胞的粗线粒体部分中发现KAT和GTK酶活性均有显著富集。
