Song I S, Yoshioka M, Erickson R H, Miura S, Guan D, Kim Y S
Gastroenterology. 1986 Nov;91(5):1234-42. doi: 10.1016/s0016-5085(86)80022-1.
Neutral metalloendopeptidase enzymes were identified and partially characterized in the brush-border membranes of rat small intestinal mucosal cells using insulin B chain and glutaryl-trialanine-4-methoxy-beta-naphthylamide as substrates. Three different molecular species of endopeptidase were identified by disc gel electrophoresis. These enzymes were shown to be distinct from pancreatic endopeptidases on the basis of the following: enrichment in the brush-border membrane fraction, site of hydrolysis of peptide substrates, sensitivity to specific proteinase inhibitors, and the presence of brush-border membrane-associated endopeptidase activity in mucosal cells of Thirty-Vella loops. Hydrolysis of the substrates was shown to be a two-step process involving initial cleavage by endopeptidase with secondary hydrolysis of the peptide products by brush-border membrane aminopeptidase N. Hydrolysis of both substrates was maximum at a neutral pH and was strongly inhibited by metal chelating agents, phosphoramidone, and amastatin. Intestinal perfusion studies using glutaryl-trialanine-4-methoxy-beta-naphthylamide suggest that these enzymes play a physiologic role in protein digestion. It was concluded that neutral endopeptidases are integral components of the intestinal brush-border membrane and work in concert with aminopeptidase N to hydrolyze dietary protein. This process may be of nutritional importance in normal subjects and those with diminished exocrine pancreatic function.
以胰岛素B链和戊二酰-丙氨酰-4-甲氧基-β-萘酰胺为底物，在大鼠小肠黏膜细胞的刷状缘膜中鉴定出中性金属内肽酶并对其进行了部分特性分析。通过圆盘凝胶电泳鉴定出三种不同分子形式的内肽酶。基于以下几点，这些酶被证明与胰腺内肽酶不同：在刷状缘膜部分的富集、肽底物的水解位点、对特定蛋白酶抑制剂的敏感性以及Thirty-Vella袢黏膜细胞中刷状缘膜相关内肽酶活性的存在。底物的水解显示为一个两步过程，包括内肽酶的初始切割以及肽产物被刷状缘膜氨肽酶N的二次水解。两种底物在中性pH下的水解最大，并且受到金属螯合剂、磷酰胺脒和抑肽酶的强烈抑制。使用戊二酰-丙氨酰-4-甲氧基-β-萘酰胺的肠道灌注研究表明，这些酶在蛋白质消化中发挥生理作用。得出的结论是，中性内肽酶是肠道刷状缘膜的组成部分，并与氨肽酶N协同作用以水解膳食蛋白质。这一过程在正常受试者和外分泌胰腺功能减退的患者中可能具有营养重要性。
