The secret behind silkworm's hardy stomachs
Until now, this enzyme has not been found in any animals, but Toru Shimada and colleagues believed this might explain the silkworm's unique diet.
The researchers scanned the silkworm genome and discovered two fructofuranosidase genes, although only one was actually expressed in the worm. This gene (BmSuc1) was, as expected, concentrated in the worm's gut, although surprisingly was also prevalent in the silk gland. When they isolated the enzyme from silkworms, the researchers found it could effectively digest sucrose.
Shimada and colleagues note that further work is needed to determine if this special enzyme is the sole reason for silkworm's resistance to mulberry toxins. It's possible that fructofuranosidases may turn up in other insects that cannot eat mulberry leaves, indicating additional factors are at work.
American Society for Biochemistry and Molecular Biology. May 2008.
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