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Journal of Lipid Research, Vol 25, 389-399, Copyright © 1984 by Lipid Research, Inc.
FJ Field
The location of cholesterol esterase in rabbit intestine was re- evaluated.
In three different experiments that were designed to eliminate
contaminating mucus and pancreatic enzymes from the lumen of the small
intestine, it was observed that the activities of cholesterol esterase and
amylase in intestinal cytosol and whole homogenate decreased in parallel
fashion. After the mucus was carefully wiped from the intestinal mucosa
prior to the preparation of cytosol, amylase and cholesterol esterase
activities decreased sevenfold. The recovery of the total activity of both
enzymes in the cytosol was approximately 15%. When the lumen of the small
intestine was filled with phosphate buffer and incubated at 37 degrees C
for 20 min, cholesterol esterase and amylase activities in the cytosol
prepared from this segment were further decreased. Moreover, the activities
of amylase and cholesterol esterase were completely recovered from the
lumen. Amylase and cholesterol esterase activities in the cytosol were
eliminated if dithiothreitol was used as a mucolytic agent to prepare
intestinal mucosa for the isolation of intestinal cells. In whole
homogenates prepared from these intestinal segments, approximately 10-15%
of the total cholesterol esterase activity remained. This activity, which
could not be accounted for by pancreatic contamination, was associated with
intestinal nuclei and cellular debris. Progesterone, ethinyl estradiol, and
25-hydroxycholesterol regulated microsomal acyl CoA:cholesterol
acyltransferase activity and caused similar directional changes in the rate
of cholesteryl ester synthesis in isolated intestinal cells. These same
sterols, however, failed to affect cytosolic cholesterol esterase activity
in vitro.
ARTICLES
Intestinal cholesterol esterase: intracellular enzyme or contamination of cytosol by pancreatic enzymes?
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