Studies on catalytic mechanism of prolyl endopeptidase by genetic method and biological significance of it in the brain

克隆了脑膜败血症黄杆菌、嗜水杆菌和牛脑的脯氨酸内肽酶[EC 3.4.21.26]基因和大肠杆菌的蛋白酶II基因。这四种酶的一级结构高度守恒。令人惊讶的是，脯氨酸内肽酶的c端区域与以下蛋白质具有显著的同源性：猪和大鼠的酰基氨基酸释放酶、人蛋白3P21、大鼠和人二肽基氨基肽酶IV、酵母二肽基氨基肽酶B和乳球菌的x -脯氨酸二肽基氨基肽酶。催化三联体的氨基酸残基是保守的。这些酶在寡肽上也有共同的特征。因此，脯氨酸寡肽酶家族被认为是一个新的丝氨酸内肽酶家族。淀粉样蛋白b/A4肽是阿尔茨海默病患者老年斑和脑血管淀粉样蛋白中典型表现的组成成分之一。本文首次用免疫染色法测定了衰老加速小鼠（SAM）体内脯氨酸内肽酶的分布。我还发现脯氨酸内肽酶和淀粉样蛋白b/A4肽在海马中的分布关系密切。这些结果表明，脯氨酸内肽酶参与了SAM脑内淀粉样蛋白沉积的形成过程。

The prolyl endopeptidase [EC 3.4.21.26] genes of Flavobacterium meningosepticum, A.hydrophila, and bovine brain, and protease II gene from E.coli were cloned. A high conservation of primary structure is observed among these four enzumes. Surprisingly, C-terminal regions of prolyl endopeptidase show significant homology to following proteins : pig and rat acyl-amino acid releasing enzymes, human protein 3P21, rat and human dipeptidyl aminopeptidases IV, yeast dipeptidyl aminopeptidase B, and X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis. The amino acid residues of the catalytic triad are well conserved. These enzymes have also common characteristics on oligopeptides. Thus, presence of prolyl oligpeptidase family was proposed as a new family of serine endopeptidases.Amyloid b/A4 peptide is one of the integral components that are typically manifested in senile plaques and cerebrovascular amyloids in the patients with Alzheimer's disease. I ascertained for the first time the distribution of prolyl endopeptidase in senescence accelerated mouse (SAM) by the immunostaining method. I also found that prolyl endopeptidase and amyloid b/A4 peptide distributed with close relationships in the hippocampus. These result suggest that prolyl endopeptidase is involved in the processes to form amyloid deposition in the brain of SAM.