Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
Biochem Pharmacol. 2010 Oct 1;80(7):1007-11. doi: 10.1016/j.bcp.2010.06.015. Epub 2010 Jun 23.
B-type natriuretic peptide (BNP) combats cardiac stress by reducing blood pressure and ventricular fibrosis. Human BNP is inactivated by unknown cell surface proteases. N-terminal cleavage of mouse BNP by the renal protease meprin A was reported to increase inactivating degradation by a second protease named neprilysin. Since the sequence surrounding the meprin A cleavage site in BNP differs between species, we tested whether meprin A degrades human BNP. Using a recently developed proteolytic bioassay, the ability of various protease inhibitors to block the inactivation of BNP was measured. In rat kidney membranes, inhibitors of meprin A or neprilysin partially or completely blocked inactivation of rat BNP(1-32) when added individually or in combination, respectively. In contrast, neither inhibitor alone or in combination prevented the inactivation of human BNP(1-32) by human kidney membranes. Leupeptin, a serine protease inhibitor, totally blocked inactivation of human BNP by human membranes, substantially blocked the inactivation of rat BNP(1-32) by human membranes, but had no effect on the inactivation of rat BNP(1-32) by rat kidney membranes. Purified neprilysin reduced the bioactivity of rat BNP(1-32) and human BNP. Digestion with both meprin and neprilysis caused the greatest reduction in rat BNP(1-32) but had no effect on the bioactivity of human BNP(1-32). We conclude that meprin A does not degrade BNP in humans and should not be considered a pharmacologic target of the natriuretic peptide system.
B 型利钠肽（BNP）通过降低血压和心室纤维化来抵抗心脏应激。人类 BNP 被未知的细胞表面蛋白酶失活。据报道，肾脏蛋白酶糜蛋白酶 A 对小鼠 BNP 的 N 端切割会增加第二种名为 Neprilysin 的蛋白酶的失活降解。由于 BNP 中糜蛋白酶 A 切割位点周围的序列在物种间存在差异，因此我们测试了糜蛋白酶 A 是否会降解人 BNP。使用最近开发的蛋白水解生物测定法，测量了各种蛋白酶抑制剂阻止 BNP 失活的能力。在大鼠肾膜中，当分别单独或组合添加时，糜蛋白酶 A 或 Neprilysin 的抑制剂部分或完全阻止了大鼠 BNP(1-32)的失活。相比之下，没有一种抑制剂单独或组合可以阻止人肾膜对人 BNP(1-32)的失活。亮肽素，一种丝氨酸蛋白酶抑制剂，完全阻止了人膜对人 BNP 的失活，大大阻止了人膜对大鼠 BNP(1-32)的失活，但对大鼠肾膜对大鼠 BNP(1-32)的失活没有影响。纯化的 Neprilysin 降低了大鼠 BNP(1-32)和人 BNP 的生物活性。糜蛋白酶和 Neprilysin 的消化导致大鼠 BNP(1-32)的最大减少，但对人 BNP(1-32)的生物活性没有影响。我们得出结论，糜蛋白酶 A 不会在人体内降解 BNP，不应被视为利钠肽系统的药理学靶点。
