title: Biochemical, structural and functional diversity between two digestive α-amylases from Helicoverpa armigera.
abstract: BACKGROUND
  Helicoverpa armigera (Lepidoptera) feeds on various plants using diverse digestive enzymes as one of the survival tool-kit. The aim of the present study was to understand biochemical properties of recombinant α-amylases of H. armigera viz., HaAmy1 and HaAmy2.
  
  
  METHODS
  The open reading frames of HaAmy1 and HaAmy2 were cloned in Pichia pastoris and expressed heterologously. Purified recombinant enzymes were characterized for their biochemical and biophysical attributes using established methods.
  
  
  RESULTS
  Sequence alignment and homology modeling showed that HaAmy1 and HaAmy2 were conserved in their amino acid sequences and structures. HaAmy1 and HaAmy2 showed optimum activity at 60°C; however, they differed in their optimum pH. Furthermore, HaAmy2 showed higher affinity for starch and amylopectin whereas HaAmy1 had higher catalytic efficiency. HaAmy1 and HaAmy2 were inhibited to the same magnitude by a synthetic amylase inhibitor (acarbose) while wheat amylase inhibitor showed about 2-fold higher inhibition of HaAmy1 than HaAmy2 at pH7 while 6-fold difference at pH11. Interactions of HaAmy1 and HaAmy2 with wheat amylase inhibitor revealed 2:1 stoichiometric ratio and much more complex interaction with HaAmy1.
  
  
  CONCLUSIONS
  The diversity of amylases in perspective of their biochemical and biophysical properties, and their differential interactions with amylase inhibitors signify the potential role of these enzymes in adaptation of H. armigera on diverse plant diets.
  
  
  CONCLUSIONS
  Characterization of digestive enzymes of H. armigera provides the molecular basis for the polyphagous nature and thus could assist in designing future strategies for the insect control.
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India.
authors.forename: Amey J
authors.initials: AJ
authors.lastname: Bhide
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India.
authors.forename: Sonal M
authors.initials: SM
authors.lastname: Channale
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India.
authors.forename: Sucheta S
authors.initials: SS
authors.lastname: Patil
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India.
authors.forename: Vidya S
authors.initials: VS
authors.lastname: Gupta
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India. Electronic address: s.ramasamy@ncl.res.in.
authors.forename: Sureshkumar
authors.initials: S
authors.lastname: Ramasamy
authors.affiliation: Plant Molecular Biology Unit, Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008 (MS), India. Electronic address: ap.giri@ncl.res.in.
authors.forename: Ashok P
authors.initials: AP
authors.lastname: Giri
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006863:Hydrogen-Ion Concentration; D007915:Lepidoptera / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein; D000516:alpha-Amylases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology
chemical_list: D000516:alpha-Amylases
keywords: Amylase inhibitors; Digestive enzymes; Enzyme activity; Helicoverpa armigera; α-amylases