title: Property of midgut α-amylase from Mythimna separata (Lepidoptera: Noctuidae) larvae and its responses to potential inhibitors in vitro.
abstract: Midgut α-amylase is an important digestive enzyme involved in larval energy metabolism and carbohydrate assimilation. In this article, the properties of midgut α-amylase from the Oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae), larvae were characterized, and its in vitro responses to chemical inhibitors were also determined. The kinetic parameters Km and Vmax of midgut α-amylase were 0.064 M, 4.81 U mg pro(-1) in phosphate buffer, and 0.128 M, 1.96 U mg pro(-1) in barbiturate-acetate buffer; α-amylase activity linearly increased as starch concentration increased. α-Amylase activity was not influenced by amino acids such as Pro, Met, Try, His, Ala, and Phe but was strongly activated by antioxidants. Reduced glutathione, 1,4-dithiothreitol, β-mercaptoethanol, and ascorbic acid improved the activity of α-amylase about 2.06, 3.46, 3.37, and 6.38 times, respectively, relative to the control. Ethylenediaminetetraacetic acid, sodium dodecyl sulfonate, and N-bromosuccinimide (NBS) strongly inhibited α-amylase. α-, β-, and γ-cyclodextrin were not the preferred substrates for α-amylase. Kinetic analysis showed that IC50 value of NBS against α-amylase was 1.52 (±0.26) µM, and the mode of action of NBS with Ki as 2.53 (0.35) µM was a mixed-type inhibition that indicated a combination of partial competitive and pure noncompetitive inhibition. The midgut α-amylase of armyworm larvae may be a potential target for novel insecticide development and pest control.
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China.
authors.forename: Wenping
authors.initials: W
authors.lastname: Xu
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China qchuang@ecust.edu.cn.
authors.forename: Qingchun
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China.
authors.forename: Xiwei
authors.initials: X
authors.lastname: Wu
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Yu
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China.
authors.forename: Xuexiao
authors.initials: X
authors.lastname: Wang
authors.affiliation: Shanghai Key Lab of Chemical Biology, School of Pharmacy, East China University of Science & Technology, Shanghai 200237, China.
authors.forename: Liming
authors.initials: L
authors.lastname: Tao
mesh_terms: D000818:Animals; D001974:Bromosuccinimide / Q000494:pharmacology*; D004064:Digestive System / Q000187:drug effects / Q000378:metabolism; D065089:Glycoside Hydrolase Inhibitors / Q000494:pharmacology*; D019476:Insect Proteins / Q000378:metabolism*; D007306:Insecticides / Q000494:pharmacology; D007700:Kinetics; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D009036:Moths / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D000516:alpha-Amylases / Q000378:metabolism*
chemical_list: D065089:Glycoside Hydrolase Inhibitors; D019476:Insect Proteins; D007306:Insecticides; D000516:alpha-Amylases; D001974:Bromosuccinimide
keywords: Mythimna separata; chemical inhibitor; midgut α-amylase