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Starch
is the major source of dietary glucose. The enzymes
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responsible
for starch degradation are called amylases.
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Other
sources of glucose are sucrose, a disaccharide
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glucose-fructose
from fruits, and lactose, a glucose-
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galactose disaccharide from milk. Only monosaccharide
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species
like glucose, fructose and galactose can be
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absorbed
via active membrane transport systems. Special
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intestinal
glucosidases split the disaccharides into their
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monosaccharide
components. Maltose is hydrolyzed by
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isomaltase
(oligo-1,6-glucosidase, E.C. 3.2.1.10) and, with
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lower
efficacy, by sucrase (sucrose alpha-glucosidase,
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E.C.
3.2.1.48). Lactose intolerance comes from a lack of
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lactase in many adults, causing an accumulation of
milk
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sugar
with consequences such as dehydration.
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