title: Physiochemical properties and kinetics of glucoamylase produced from deoxy-d-glucose resistant mutant ofAspergillus nigerfor soluble starch hydrolysis.
abstract: Glucoamylases (GAs) from a wild and a deoxy-d-glucose-resistant mutant of a locally isolatedAspergillus nigerwere purified to apparent homogeneity. The subunit molecular mass estimated by SDS-PAGE was 93 kDa for both strains, while the molecular masses determined by MALDI-TOF for wild and mutant GAs were 72.876 and 72.063 kDa, respectively. The monomeric nature of the enzymes was confirmed through activity staining. Significant improvement was observed in the kinetic properties of the mutant GA relative to the wild type enzyme. Kinetic constants of starch hydrolysis forA. nigerparent and mutant GAs calculated on the basis of molecular masses determined through MALDI-TOF were as follows:kcat= 343 and 727 s-1,Km= 0.25 and 0.16 mg mL-1,kcat/Km(specificity constant) = 1374 and 4510 mg mL-1s-1, respectively. Thermodynamic parameters for soluble starch hydrolysis also suggested that mutant GA was more efficient compared to the parent enzyme.
authors.affiliation: Department of Food Science and Technology, University College of Agriculture, Bahauddin Zakariya University, Multan, Pakistan ; Enzyme Engineering Lab, National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Riaz
authors.forename: Muhammad Hamid
authors.initials: MH
authors.lastname: Rashid
authors.forename: Lindsay
authors.initials: L
authors.lastname: Sawyer
authors.forename: Saeed
authors.initials: S
authors.lastname: Akhtar
authors.forename: Muhammad Rizwan
authors.initials: MR
authors.lastname: Javed
authors.forename: Habibullah
authors.initials: H
authors.lastname: Nadeem
authors.forename: Martin
authors.initials: M
authors.lastname: Wear
keywords: Activity staining; Aspergillus niger; Glucoamylase; Purification; Starch hydrolysis