title: Structural and biochemical features of acidic α-amylase of Bacillus acidicola.
abstract: The investigation is aimed at understanding structure-function aspect of α-amylase of an acidophilic bacterium Bacillus acidicola (BAamy), which is Ca(2+)-independent and active at acidic pH of native starch, and thus, suits better in starch saccharification process. The CD spectroscopic data analysis revealed that the enzyme has 30% α-helices, 14.2% β-sheets, and 55.8% random coils at 60 °C and pH 4.0. Using Bacillus stearothermophilus α-amylase (BStA) as the template, 3-D structure of rBAamy has been proposed. A complete loss in α-amylase activity was recorded when the amino acid residues (D231, E261 and D328) were substituted that confirmed their role in catalysis. The CD studies indicated a decrease in the α-helices content below and beyond the optimum pH and temperature that suggests a critical role of α-helix in maintaining the structural conformation of the enzyme. Fluorescence-quenching by N-bromosuccinimide (NBS) suggested the role of tryptophan in maintaining structural integrity of α-amylase and that by acrylamide indicated interaction by simple collision process.
authors: Department of Microbiology, University of Delhi, South Campus, Benito, Juarez Road, New Delhi 110021, India.
authors: Archana
authors: A
authors: Sharma
authors: T
authors: T
authors: Satyanarayana
mesh_terms: D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D020134:Catalytic Domain; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017433:Protein Structure, Secondary / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013696:Temperature; D000516:alpha-Amylases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D000516:alpha-Amylases
keywords: Bacillus acidicola; Circular dichroism; Fluorescence quenching; Site-directed mutagenesis; α-Amylase