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

克隆了脑膜败血黄杆菌、A. peglia和牛脑的脯氨酰内肽酶[EC 3.4.21.26]基因以及大肠杆菌的蛋白酶II基因。这四种昆虫的一级结构具有很高的保守性。令人惊讶的是，脯氨酰内肽酶的C-末端区域显示出与以下蛋白质的显著同源性：猪和大鼠酰基氨基酸释放酶、人蛋白3 P21、大鼠和人二肽基氨基肽酶IV、酵母二肽基氨基肽酶B和来自乳酸乳球菌的X-脯氨酰二肽基氨基肽酶。催化三联体的氨基酸残基是很保守的。这些酶在寡肽上也具有共同的特征。淀粉样蛋白B/A4肽是老年斑和阿尔茨海默病患者脑血管淀粉样蛋白的典型组成成分之一。本文首次用免疫组织化学染色法确定了脯氨酰内肽酶在快速老化小鼠（SAM）体内的分布。同时发现脯氨酰内肽酶和淀粉样蛋白B/A4肽在海马的分布关系密切。提示脯氨酰内肽酶参与了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.