Miyagi T, Hata K, Konno K, Tsuiki S
Biochemistry Laboratory, Tohoku University, Sendai, Japan.
Tohoku J Exp Med. 1992 Oct;168(2):223-9. doi: 10.1620/tjem.168.223.
We have demonstrated that rat liver contains at least four types of sialidase differing in subcellular location, in catalytic property and immunologically. They are intralysosomal, cytosolic and membrane-associated sialidases I and II. Membrane sialidase I locates mainly in plasma membrane and sialidase II in lysosomal membrane. Immunological study reveals that the same types of sialidase exist in various tissues of rat and of other mammalian species. Based on these results, we examined the sialidases in rat hepatomas and in transformed cells of JB6 mouse epidermal cell. Hepatomas were found to possess four types of sialidase and the three of them altered quantitatively. Intralysosomal sialidase activity was higher but cytosolic and lysosomal membrane sialidase activities were lower in hepatomas than in control liver. When the sialidases of transformants of JB6 cells were compared with those of control cells, the activities of two lysosomal sialidases were decreased and contrarily plasma membrane sialidase was increased. We discussed a possible significance of the sialidase alterations in carcinogenesis.
我们已经证明，大鼠肝脏中至少含有四种唾液酸酶，它们在亚细胞定位、催化特性和免疫特性方面存在差异。它们是溶酶体内、胞质以及与膜相关的唾液酸酶I和II。膜唾液酸酶I主要位于质膜，唾液酸酶II位于溶酶体膜。免疫学研究表明，大鼠和其他哺乳动物物种的各种组织中存在相同类型的唾液酸酶。基于这些结果，我们检测了大鼠肝癌组织和JB6小鼠表皮细胞转化细胞中的唾液酸酶。发现肝癌组织含有四种唾液酸酶，其中三种在数量上发生了变化。与对照肝脏相比，肝癌组织中溶酶体内唾液酸酶活性较高，但胞质和溶酶体膜唾液酸酶活性较低。当将JB6细胞转化体的唾液酸酶与对照细胞的唾液酸酶进行比较时，两种溶酶体唾液酸酶的活性降低，相反，质膜唾液酸酶活性增加。我们讨论了唾液酸酶改变在致癌过程中的可能意义。
