Layer, P.; Carlson, G. L.; DiMagno, E.
P.
JOURNAL NAME- Gastroenterology
VOL. 88
1985 Jun
PP. 1895-902
DOCUMENT TYPE- Journal
Article
JOURNAL CODE- 0374630
JOURNAL SUBSET- MEDJSAIM;
MEDJSIM
ISSN- 0016-5085
PUBLICATION COUNTRY-
UNITED STATES
LANGUAGE- English NDN-
239-0020-4228-2
Whether commercial, bean-derived alpha-amylase
inhibitor preparations failed to decrease
starch digestion in humans because of
insufficient antiamylase activity, destruction
by gastrointestinal secretions, or decreased
activity in the presence of starch is
unknown. We used a simple partial purification
procedure to markedly concentrate the
inhibitor (sixfold to eightfold by total
protein content, and 30-40-fold by dry
weight). Compared with a commercial preparation
and crude bean extract, this partially
purified inhibitor inactivated intraduodenal,
intraileal, and salivary amylase in vitro
faster and more completely (p less than
0.001); its specific activity was not
affected by exposure to gastric juice
and was only minimally reduced by duodenal
juice. Whereas the rate of amylase inhibition
by inhibitor was markedly slowed in the
presence of nondietary liquid starch,
dietary solid starch had only a minimal
effect. Consequently, the partially purified
inhibitor had no effect on liquid starch
digestion, but decreased in vitro digestion
of dietary starch in a dose-dependent
manner (p less than 0.001). Perfusion
of the partially purified inhibitor (2.0,
3.5, or 5.0 mg/ml at 5 ml/min) into the
duodenum of humans rapidly inhibited greater
than 94%, greater than 99%, or greater
than 99.9% of intraluminal amylase activity.
We conclude that commercial amylase inhibitors
failed to decrease starch digestion in
vivo mainly because they have insufficient
antiamylase activity. However, a partially
purified inhibitor with increased specific
activity is stable in human gastrointestinal
secretions, slows dietary starch digestion
in vitro, rapidly inactivates amylase
in the human intestinal lumen, and, at
acceptable oral doses, may decrease intraluminal
digestion of starch in humans. Such an
inhibitor therefore deserves study.
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