title: Kinetic and thermodynamic studies of a novel acid protease from Aspergillus foetidus.
abstract: The kinetics of a thermostable extracellular acid protease produced by an Aspergillus foetidus strain was investigated at different pH, temperatures and substrate concentrations. The enzyme exhibited maximal activity at pH 5.0 and 55°C, and its irreversible deactivation was well described by first-order kinetics. When temperature was raised from 55 to 70°C, the deactivation rate constant increased from 0.018 to 5.06h(-1), while the half-life decreased from 37.6 to 0.13h. The results of activity collected at different temperatures were then used to estimate, the activation energy of the hydrolysis reaction (E*=19.03kJ/mol) and the standard enthalpy variation of reversible enzyme unfolding (ΔH°U=19.03kJ/mol). The results of residual activity tests carried out in the temperature range 55-70°C allowed estimating the activation energy (E(*)d=314.12kJ/mol), enthalpy (311.27≤(ΔH°d≤311.39kJ/mol), entropy (599.59≤ΔS(*)d≤610.49kJ/mol K) and Gibbs free energy (103.18≤ΔG(*)d≤113.87kJ/mol) of the enzyme irreversible denaturation. These thermodynamic parameters suggest that this new protease is highly thermostable and could be important for industrial applications. To the best of our knowledge, this is the first report on thermodynamic parameters of an acid protease produced by A. foetidus.
authors.affiliation: Department of Biochemical and Pharmaceutical Technology, University of São Paulo, São Paulo, SP, 05508-000, Brazil. Electronic address: paulasouza@usp.br.
authors.forename: Paula Monteiro
authors.initials: PM
authors.lastname: Souza
authors.affiliation: Department of Civil, Chemical and Environmental Engineering, Pole of Chemical Engineering, Genoa University, via Opera Pia 15, 16145 Genoa, Italy.
authors.forename: Bahar
authors.initials: B
authors.lastname: Aliakbarian
authors.affiliation: Laboratory of Enzymology, Department of Cellular Biology, University of Brasilia, Campus Darcy Ribeiro, Asa Norte, Brasilia, DF, 70910900, Brazil.
authors.forename: Edivaldo Ximenes Ferreira
authors.initials: EX
authors.lastname: Filho
authors.affiliation: Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Campus Darcy Ribeiro, Asa Norte, Brasilia, DF, 70910900, Brazil.
authors.forename: Pérola Oliveira
authors.initials: PO
authors.lastname: Magalhães
authors.affiliation: Department of Biochemical and Pharmaceutical Technology, University of São Paulo, São Paulo, SP, 05508-000, Brazil.
authors.forename: Adalberto Pessoa
authors.initials: AP
authors.lastname: Junior
authors.affiliation: Department of Civil, Chemical and Environmental Engineering, Pole of Chemical Engineering, Genoa University, via Opera Pia 15, 16145 Genoa, Italy.
authors.forename: Attilio
authors.initials: A
authors.lastname: Converti
authors.affiliation: Department of Civil, Chemical and Environmental Engineering, Pole of Chemical Engineering, Genoa University, via Opera Pia 15, 16145 Genoa, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Perego
mesh_terms: D001230:Aspergillus / Q000201:enzymology*; D002364:Caseins / Q000737:chemistry; D004789:Enzyme Activation; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D010447:Peptide Hydrolases / Q000737:chemistry*; D013379:Substrate Specificity; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002364:Caseins; C026018:azocasein; D010447:Peptide Hydrolases
keywords: Acid protease; Aspergillus foetidus; Thermostability