Absorption of toxic β-glucosides produced by plants and their effect on tissue trehalases from insects

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology Vol. 143; no. 3; pp. 367 - 373
• Main Authors: Silva, Maria C.P., Terra, Walter R., Ferreira, Clélia
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-03-2006
• Subjects: Amygdalin; Animals; Coleoptera; Diatraea saccharalis; Diptera; Enzyme Inhibitors - isolation & purification; Enzyme Inhibitors - toxicity; Esculin; Glucosides - isolation & purification; Glucosides - toxicity; Insecta - drug effects; Insecta - enzymology; Lepidoptera; Midgut trehalase; Musca domestica; Noctuidae; Phlorizin; Plant β-glucosides; Plants - chemistry; Prunasin; Spodoptera frugiperda; Tenebrio molitor; Tenebrionidae; Trehalase - analysis; Trehalase - antagonists & inhibitors; Trehalase inhibition; β-glucosidase effects; β-glucoside absorption; β-glucoside absorption; Trehalase inhibition; Phlorizin; Midgut trehalase; Plant β-glucosides; Esculin; Prunasin; β-glucosidase effects; Amygdalin
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/j.cbpb.2005.12.011

Trehalases present in body wall, Malpighian tubules, fat body, midgut and haemolymph from
Tenebrio molitor (Coleoptera),
Musca domestica (Diptera),
Spodoptera frugiperda and
Diatraea saccharalis (Lepidoptera) were assayed in the presence and absence of toxic β-glucosides produced by plants or their aglycones. The glucosides used were phlorizin, amygdalin, prunasin and the aglycone mandelonitrile. In addition,
T. molitor and
S. frugiperda trehalases were assayed with and without esculin. More than 60% of total trehalase activity was found in the midgut of these insects. As a rule, trehalases present in each insect were inhibited by at least two of the glucosides. Prunasin was the best inhibitor in tissues with highest trehalase activity.
S. frugiperda β-glucosidases were not able to hydrolyze esculin. Nevertheless, their larval midguts absorb the intact glucoside that is recovered from the fat body, Malpighian tubules and mainly from haemolymph. Mature larvae fed on a diet containing 3 mM (0.1%) esculin have 0.2 mM esculin in their haemolymph, and weigh 60% of control larvae. In vitro, haemolymph trehalase activity is abolished by 0.5 mM esculin. This inhibition may play a role in the decrease of body weight and in animal survival.
S. frugiperda larvae reared in 0.1% amygdalin-containing diet present higher trehalase activity in tissues than the larvae reared in 0.1% esculin-containing diet. Higher trehalase activity should be the reason why the
S. frugiperda development is not impaired by 1% dietary amygdalin, in contrast to what is observed when insects are reared in 0.1% esculin. The data suggest that many plant β-glucosides are toxic because they inhibit trehalase, a key enzyme controlling glucose availability in insects.