A novel sucrose hydrolase from the bombycoid silkworms Bombyx mori, Trilocha varians, and Samia cynthia ricini with a substrate specificity for sucrose.
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.
Laboratory of Insect Genetics and Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan; College of Animal Sciences, Zhejiang University, China.
Huabing
H
Wang
Laboratory of Insect Genetics and Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.
Takashi
T
Kiuchi
Laboratory of Insect Genetics and Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.
Susumu
S
Katsuma
Laboratory of Insect Genetics and Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan. Electronic address: shimada@ss.ab.a.u-tokyo.ac.jp.
Toru
T
Shimada
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D012831:Bombyx / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D041981:Gastrointestinal Tract / Q000201:enzymology; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000201:enzymology / Q000235:genetics; D031625:Morus / Q000737:chemistry / Q000145:classification; D009036:Moths / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D013045:Species Specificity; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism*
D000470:Alkaloids; D019476:Insect Proteins; D013395:Sucrose; D006026:Glycoside Hydrolases
Lepidoptera; Sucrose; Sucrose hydrolase; Sugar-mimic alkaloids