Recent evidence indicates that the homeostatic balance between
elastase and
antiprotease activity is altered in the infrarenal aorta of those patients with different types of aortic pathologic findings. The specific properties of
elastase found in the aorta of patients with
abdominal aortic aneurysms (AAA) are discussed herein. Activity of
elastase extracted from ten pooled AAA specimens was observed when incubated with several inhibitors: 13.2 per cent for phenyl-suphonyl flouride (PSF); 43.3 per cent for
ethylenediaminetetraacetic acid (
EDTA); 77.7 per cent for
pepstatin; 137.0 per cent for
leupeptin, and 24.0 per cent for alpha-1-antitrypsin. Irreversible inhibition by PSF indicates that the
elastase is a
serine protease. The
elastase is most likely not a metallo
enzyme, since it had no absolute requirement for
divalent cations as indicated by only partial inhibition by
EDTA.
Elastase activity is most likely not due to
cathepsins B or D, since
cathepsins are active in an
acid pH and selectively inhibited by
leupeptin and
pepstatin. The pH curve revealed a maximum activity at pH 8.2 and
elastase activity was significantly inhibited by alpha-1-antitrypsin in a dose response manner determining functional
elastase activity. These data indicate that the
elastase in the aorta of patients with an AAA has the exact properties of the
serine elastase found in the smooth muscle cells of the aorta in rats. These results also confirm the critical role of alpha-1-antitrypsin in determining functional
elastase activity. Smooth muscle cell regulation of
elastin metabolism may be important in determining why some patients have AAA and others have occlusive
aortic disease develop.