A novel sucrose hydrolase from the bombycoid silkworms Bombyx mori,Trilocha varians,and Samia cynthia ricini with a substrate specificity for sucrose |
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Affiliation: | 1. Department of Pharmacy, Oregon Health & Science University, Portland, OR 97239;2. Department of Pharmacy, University Health System and Department of Emergency Medicine, University of Texas Health Science Center San Antonio, San Antonio, TX 78229;3. Department of Pharmacy, University of Vermont Medical Center, Burlington, VT 05402;4. Department of Surgery, Oregon Health & Science University, Portland, OR 97239 |
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Abstract: | Although membrane-associated sucrase activity has been detected in the midgut of various lepidopteran species, it has not yet been identified and characterized at the molecular level. In the present study, we identified a novel sucrose hydrolase (SUH) gene from the following three bombycoid silkworms: Bombyx mori, Trilocha varians, and Samia cynthia ricini and named them BmSuh, TvSuh, and ScSuh, respectively. The EST dataset showed that BmSuh is one of the major glycoside hydrolase genes in the larval midgut of B. mori. These genes were almost exclusively expressed in the larval midgut in all three species, mainly at the feeding stage. SUHs are classified into the glycoside hydrolase family 13 and show significant homology to insect maltases. Enzymatic assays revealed that recombinant SUHs were distinct from conventional maltases and exhibited substrate specificity for sucrose. The recombinant BmSUH was less sensitive to sugar-mimic alkaloids than TvSUH and ScSUH, which may explain the reason why the sucrase activity in the B. mori midgut was less affected by the sugar-mimic alkaloids derived from mulberry. |
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Keywords: | Sucrose hydrolase Lepidoptera Sugar-mimic alkaloids Sucrose |
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