PURIFICATION AND CHARACTERIZATION OF ENDOTHELIN-1 DEGRADATION ACTIVITY FROM PORCINE KIDNEY

In order to identify the membrane-bound peptidase that is responsible for the degradation of endothelin (ET), an endothelin-1 (ET-1) degrada tion enzyme was solubilized from membrane fractions of porcine kidney with 1% Triton X-100, and subsequently purified by column chromatograp hies, i.e., diethylamino-Sepharose ion exchange, gel permeation, Con A Sepharose and hydroxyapatite chromatography. On DEAE-Toyopearl ion ex change column chromatography, the ET degradation enzyme and aminopepti dase were separated, but ET degradation enkephalinase activities were not separable. In order to separate ET degradation enzyme and enkephal inase, the active fractions were loaded on each of the column chromato graphies: sephacryl S-200, Con A Sepharose or hydroxyapatite. The ET d egradation activities were co-migrated with enkephalinase activities o n all of the three chromatographies. In addition, the ET degradation a ctivities were inhibited by thiorphan, phosphoramidon and EDTA, which are known to inhibit enkephalinase. These results suggest that ET degr adation activity in the membrane fractions of the kidney is related to enkephalinase and may be involved in the degradation of ET-1 in vivo.