title: Characteristics of a high maltose-forming, acid-stable, and Ca(2+)-independent α-amylase of the acidophilic Bacillus acidicola.
abstract: The purified acidic α-amylase of Bacillus acidicola is a monomer of 66.0 kDa, optimally active at pH 4.0 and 60 °C. The enzyme is Ca2+ independent with T1/2 for 18 min at 80 °C. The Km, Vmax, and catalytic efficiency (kcat/Km) of the enzyme are 1.6 mg mL(−1), 23.8 μmol mg(−1) min(−1), and 981 μmol s(−1), respectively. Among detergents, Tween 20, 40, and 80 stimulated enzyme activity, whereas sodium dodecyl sulfate and Triton X-100 inhibited even at low concentration. EGTA has not affected the activity, whereas EDTA β-mercaptoethanol, iodoacetic acid, and Dithiothreitol exhibited a slight inhibitory action. Phenylmethanesulfonyl fluoride, N-bromosuccinimide, and Hg2+ strongly inhibited enzyme activity. The experimental activation energy and temperature quotient are 50.12 kJ mol(−1) and 1.37. When thermodynamic parameters (ΔH and ΔS) of the enzyme have been determined at different temperatures, ΔG is positive suggesting that the enzyme is thermostable. The enzyme hydrolyzes raw starches, and therefore, the enzyme finds application in raw starch saccharification at sub-gelatinization temperatures that saves energy needed for gelatinization of raw starch at 105 °C.
authors.forename: Archana
authors.initials: A
authors.lastname: Sharma
authors.forename: T
authors.initials: T
authors.lastname: Satyanarayana
mesh_terms: D000143:Acids / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008320:Maltose / Q000096:biosynthesis*; D055550:Protein Stability; D013213:Starch; D013379:Substrate Specificity; D013696:Temperature; D000516:alpha-Amylases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D000143:Acids; D008320:Maltose; D013213:Starch; D000516:alpha-Amylases; D002118:Calcium