Xu Y, Wellner D, Scheinberg D A
Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
Biochem Biophys Res Commun. 1995 Mar 17;208(2):664-74. doi: 10.1006/bbrc.1995.1390.
Aminopeptidase N (EC 3.4.11.2) is an important enzyme that is involved in the degradation of regulatory peptides including enkephalins. We report here that purified and native membrane-bound aminopeptidase N will sequentially and completely hydrolyze both Leu-enkephalin and Met-enkephalin from the amino terminus. Both purified pig aminopeptidase N and the enzyme on live HL60 cells displayed similar Km values for enkephalin. The naturally occurring neuropeptides substance P and bradykinin, and the morphine agonist, morphiceptin, were not hydrolyzed by aminopeptidase N and each inhibited the enzymatic activity. Each of these peptides contains a proline at the second residue. The Ki values for substance P (0.44 microM), bradykinin (9.4 microM), and morphiceptin (169 microM) were obtained with the enzyme on live HL60 cells. The values for the purified enzyme from pig were similar. The potent inhibition of aminopeptidase N by substance P and bradykinin suggests that these peptides may be natural inhibitors of the enzyme.
氨肽酶N（EC 3.4.11.2）是一种重要的酶，参与包括脑啡肽在内的调节肽的降解。我们在此报告，纯化的天然膜结合氨肽酶N将从氨基末端依次并完全水解亮氨酸脑啡肽和甲硫氨酸脑啡肽。纯化的猪氨肽酶N和活HL60细胞上的该酶对脑啡肽显示出相似的Km值。天然存在的神经肽P物质和缓激肽以及吗啡激动剂吗啡肽均未被氨肽酶N水解，且每种都抑制酶活性。这些肽中的每一种在第二个残基处都含有一个脯氨酸。用活HL60细胞上的酶获得了P物质（0.44 microM）、缓激肽（9.4 microM）和吗啡肽（169 microM）的Ki值。来自猪的纯化酶的值相似。P物质和缓激肽对氨肽酶N的有效抑制表明这些肽可能是该酶的天然抑制剂。
