Cruz C, Charli J L, Vargas M A, Joseph-Bravo P
Departamento de Bioquímica, Centro de Investigación sobre Ingeniería Genética y Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca.
J Neurochem. 1991 May;56(5):1594-601. doi: 10.1111/j.1471-4159.1991.tb02056.x.
Pyroglutamate aminopeptidase II is a highly specific membrane-bound ectopeptidase proposed to inactivate thyrotropin releasing hormone (TRH) in brain extracellular space. Its activity was measured in primary cell cultures of fetal brain in an attempt to define its cellular localization. Enzyme activity was detected in hypothalamic or cortical cell membrane fractions from 4- to 12-day-old cultures. When proliferation of nonneuronal cells was abolished by cytosine arabinoside treatment, pyroglutamate aminopeptidase II specific activity was increased as compared to untreated cultures, the opposite was observed for pyroglutamate amino-peptidase I activity. Treatment of cortical cells with the neurotoxic agent glutamate reduced simultaneously pyroglutamate aminopeptidase II and glutamate decarboxylase activities. Glial cell cultures expressed pyroglutamate aminopeptidase I or glutamate synthase activities but not pyroglutamate aminopeptidase II. The data suggest that pyroglutamate aminopeptidase II is predominantly localized in neuronal cells. This is consistent with a role for pyroglutamate aminopeptidase II in TRH-ergic synaptic transmission.
焦谷氨酸氨肽酶II是一种高度特异性的膜结合外肽酶，被认为可使脑细胞外空间中的促甲状腺激素释放激素（TRH）失活。为了确定其细胞定位，在胎脑原代细胞培养物中检测了它的活性。在4至12天大的培养物的下丘脑或皮质细胞膜组分中检测到了酶活性。当用阿糖胞苷处理消除非神经元细胞的增殖时，与未处理的培养物相比，焦谷氨酸氨肽酶II的比活性增加，而焦谷氨酸氨肽酶I的活性则相反。用神经毒性剂谷氨酸处理皮质细胞会同时降低焦谷氨酸氨肽酶II和谷氨酸脱羧酶的活性。胶质细胞培养物表达焦谷氨酸氨肽酶I或谷氨酸合酶活性，但不表达焦谷氨酸氨肽酶II。数据表明，焦谷氨酸氨肽酶II主要定位于神经元细胞。这与焦谷氨酸氨肽酶II在促甲状腺激素释放激素能突触传递中的作用一致。
