Mca-RPPGFSAFK(Dnp)-OH, also known as Mca-(Ala7,Lys(Dnp)9)-bradykinin is a very sensitive fluorescent substrate for endothelin-converting enzyme-1 (ECE-1), the membrane-bound zinc metallopeptidase that is related to neprilysin. Mca-RPPGFSAFK(Dnp)-OH can a