CLEAVAGE OF ATRIAL-NATRIURETIC-PEPTIDE BY A KIDNEY MEMBRANE-BOUND CARBOXYPEPTIDASE-A

An enzymatic activity that cleaved the C-terminal Tyr of ANP (1-28) wa s characterized in human kidney microvillar membranes by using I-125-l abeled rat ANP as substrate. This activity was inhibited by potato car boxypeptidase inhibitor (PCI) and 1.10 phenanthroline, suggesting that it corresponded to a metallocarboxypeptidase, Solubilization experime nts indicated that the carboxypeptidase activity could be recovered in the supernatant after 1% Triton X-100 extraction. As separation by io n exchange chromatography revealed several peaks of enzyme activity, P CI coupled to Sepharose was used for purification. This step resulted in a single protein band at 30 kDa, as analyzed by SDS-PAGE. (C) 1998 Elsevier Science Inc.