Charli J L, Cruz C, Vargas M A, Joseph-Bravo P
Departmento de Bioquimica, Centro de Investigaciones sobre Ingenieria Genetica y Biotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 510-3, Cuernavaca, Mor. 62270, Mexico.
Neurochem Int. 1988;13(2):237-42. doi: 10.1016/0197-0186(88)90060-5.
In order to determine the pathway of extracellular metabolism of the thyrotropin releasing hormone (pyroglu-his-proNH(2)) in brain, the topographical organization of pyroglutamate aminopeptidase II on the plasma membrane was investigated. Its activity was only slightly increased when intact brain synaptosomes were lysed by osmotic shock or detergent treatment. Trypsin treatment of intact synaptosomes destroyed 70-80% of enzyme activity without affecting lactate dehydrogenase. Pyroglutamate aminopeptidase II activity was present in primary cultures of foetal mice cortical cells. It was detected in intact cells, was not released by the cells and its activity was not increased by saponin pretreatment. Trypsin treatment of the cells reduced pyroglutamate aminopeptidase II by 70% but did not affect pyroglutamate aminopeptidase I and lactate dehydrogenase. These data support that brain pyroglutamate aminopeptidase II is an ectoenzyme. They suggest that this enzyme could be responsible for thyrotropin releasing hormone extracellular catabolism in brain.
为了确定促甲状腺激素释放激素（焦谷氨酸-组氨酸-脯氨酰胺）在脑内的细胞外代谢途径，对质膜上焦谷氨酸氨肽酶II的拓扑结构进行了研究。当完整的脑突触体通过渗透压休克或去污剂处理裂解时，其活性仅略有增加。用胰蛋白酶处理完整的突触体可破坏70-80%的酶活性，而不影响乳酸脱氢酶。焦谷氨酸氨肽酶II活性存在于胎鼠皮质细胞的原代培养物中。在完整细胞中可检测到该酶，细胞不会释放该酶，且皂苷预处理不会增加其活性。用胰蛋白酶处理细胞可使焦谷氨酸氨肽酶II减少70%，但不影响焦谷氨酸氨肽酶I和乳酸脱氢酶。这些数据支持脑内焦谷氨酸氨肽酶II是一种外切酶。它们表明该酶可能负责脑内促甲状腺激素释放激素的细胞外分解代谢。
