HUMAN ENDOTHELIN-CONVERTING ENZYME (ECE-1) - 3 ISOFORMS WITH DISTINCTSUBCELLULAR LOCALIZATIONS

Citation
A. Schweizer et al., HUMAN ENDOTHELIN-CONVERTING ENZYME (ECE-1) - 3 ISOFORMS WITH DISTINCTSUBCELLULAR LOCALIZATIONS, Biochemical journal, 328, 1997, pp. 871-877
Citations number
28
Journal title
ISSN journal
02646021
Volume
328
Year of publication
1997
Part
3
Pages
871 - 877
Database
ISI
SICI code
0264-6021(1997)328:<871:HEE(-3>2.0.ZU;2-Z
Abstract
Endothelin-converting enzyme 1 (ECE-1) is a membrane-bound metalloprot ease that catalyses the conversion of inactive big endothelins into ac tive endothelins. Two different isoforms (ECE-1a and ECE-1b) have prev iously been identified for human ECE-1. In the present study we have c loned a novel human ECE-1 isoform, termed ECE-1c, and have thus shown for the first time the existence of three distinct ECE-1 isoforms. The three isoforms differ only in their N-terminal regions and are derive d from a single gene through the use of alternative promoters. Ribonuc lease protection experiments revealed that, although the relative leve ls of the three isoform mRNA species vary between human tissues, ECE-1 c mRNA is generally the predominant isoform messenger. Immunofluoresce nce microscopy analysis showed distinct subcellular localizations for the three isoforms: whereas ECE-1a and ECE-1c are localized at the cel l surface, ECE-1b was found to be intracellular and showed significant colocalization with a marker protein for the trans-Golgi network. We determined that the three isoforms have similar kinetic rate constants (K-m, k(cat) and V-max) for the processing of big endothelin 1 and th at the big endothelin isoforms 1, 2 and 3 are cleaved with similar rel ative velocities of 1.0:0.1:0.1 by the three isoenzymes.