Study on Physiological Roles of Neuropeptidases

神经肽在突触的生理作用是通过膜结合的蛋白酶的酶降解而终止的。我们已经定义、纯化和表征了四种神经肽，P物质、LHRH(黄体生成素释放激素)、强啡肽和生长抑素的膜结合蛋白。1.对培养的大鼠胎脑神经细胞对P物质的降解进行了分析，发现一种与我们从大鼠脑中纯化的P物质降解酶的性质几乎相同的金属内肽酶参与了P物质的降解，可能与神经母细胞瘤细胞和大鼠突触膜的降解有关。另一方面，研究发现内肽酶-24.11在胶质瘤细胞和培养的大鼠胎脑神经胶质细胞的降解中起作用。后一种酶是从胶质瘤细胞中纯化出来的。2.从神经母细胞瘤细胞和大鼠脑突触膜中分离纯化了在LHRH降解初期起重要作用的LHRH片段(1-5)生成酶。该酶被认为是一种金属内肽酶，其巯基是维持活性所必需的。研究还发现，类似的酶在培养的大鼠胎脑神经元和神经胶质细胞的降解过程中起着重要的作用。3.两种强啡肽降解半胱氨酸蛋白酶中的一种对四种碱性残基中的Arg-Argond具有高度的专一性。4.大鼠海马区突触膜生长抑素的降解最初是由内肽酶-24.11作用触发的。

The physiological action of neuropeptides at the synape is terminated through enzymatic degradation by membrane-bound proteases. We have defined, purified, and characterized membrane-bound proteases functioning in degradation of four neuropeptides, substance P, LHRH (luteinizing hormone-releasing hormone), dynorphin, and somatostatin. 1. We have analyzed the degradation of substance P by neuronal cells cultured from rat fetal brain and found that a metallo-endopeptidase showing properties almost identical with those of the substance P-degrading enzyme purified from rat brain by us is involved in the degradation likely as the degradation by neuroblastoma cells and rat synaptic membrane. On the other hand, it was found that endopeptidase-24.11 functions in the degradation by glioma cells and glial cells cultured from rat fetal brain. The latter enzyme has been purified from glioma cells. 2. LHRH fragment (1-5)-generating enzyme that plays an important role in the initial stage of LHRH-degradation haed been purified from neuroblastoma cells and rat brain synaptic membrane. The enzyme has been characterized as a metallo-endopeptidase whose sulfhydryl groups are essential for the maintenance of the activity. It was also found that similar enzymes play important roles in degradation by neuronal and glial cells cultured from rat fetal brain. 3. One of two dynorphin-degrading cysteine proteases has been characterized as a novel enzyme with highly strict specificity toward only Arg-Argbond among four kinds of paired basic residues. 4. The degradation of somatostatin in the rat hippocampal synaptic membranes was found to be initially triggerd by the action of endopeptidase-24.11.