ENDOTHELIN-2 CONVERTING-ENZYME FROM HUMAN RENAL ADENOCARCINOMA CELLS IS A PHOSPHORAMIDON-SENSITIVE, MEMBRANE-BOUND METALLOPROTEASE

From the membrane fraction of cultured human renal adenocarcinoma (ACH N) cells, two endothelin-2-converting enzymes (ECE-2A and ECE-2B) were solubilized with detergent Lubrol PX and separated by hydrophobic but yl fast-performance liquid chromatography. The pH range of the convert ing activity of ECE-2B for big endothelin-1 (big ET-1), big ET-2, or b ig ET-3, was very narrow, and the optimal pH for each substrate was si gnificantly different; the pH optimum for big ET-1 was 6.8 and that fo r big ET-2 or big ET-3 was 6.4. The ET-converting activity was abolish ed by phosphoramidon, 1, 10-phenanthroline and EDTA but was not inhibi ted by thiorphan, E-64, leupeptin, PCMS, p-APMSF, or pepstatin A. The conversion efficiency for big ET-2 or big ET-3 by ECE-2B was approxima tely one-eighth of that for big ET-1. The molecular weight of ECE-2B w as estimated to be 400 kDa by gel filtration. Because these characteri stics of ECE-2B are very similar to those of ET-1-converting enzyme (E CE-1) in endothelial cells, these results raise the possibility that E CE-2B is identical to ECE-1 and that a single ECE physiologically conv erts all big ETs to the corresponding ETs in ET-producing cells.