title: Biochemical properties of Cu/Zn-superoxide dismutase from fungal strain Aspergillus niger 26.
abstract: The fungal strain Aspergillus niger produces two superoxide dismutases, Cu/Zn-SOD and Mn-SOD. The primary structure of the Cu/Zn-SOD has been determined by Edman degradation of peptide fragments derived from proteolytic digests. A single chain of the protein, consisting of 153 amino acid residues, reveals a very high degree of structural homology with the amino acid sequences of other Aspergillus Cu/Zn-SODs. The molecular mass of ANSOD, measured by MALDI-MS and ESI-MS, and calculated by its amino acid sequence, was determined to be 15821 Da. Only one Trp residue, at position 32, and one disulfide bridge were identified. However, neither a Tyr residue nor a carbohydrate chain occupying an N-linkage site (-Asn-Ile-Thr-) were found. Studies on the temperature and pH dependence of fluorescence, and on the temperature dependence of CD spectroscopic properties, confirmed that the enzyme is very stable, which can be explained by the stabilising effect of the disulfide bridge. The enzyme retains about 53% of its activity after incubation for a period of 30 min at 60 degrees C, and 15% at 85 degrees C.
authors.affiliation: Interfacultary Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, D-72076 Tübingen, Germany.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Dolashki
authors.forename: Radoslav
authors.initials: R
authors.lastname: Abrashev
authors.forename: Stefan
authors.initials: S
authors.lastname: Stevanovic
authors.forename: Lilyana
authors.initials: L
authors.lastname: Stefanova
authors.forename: Syed Abid
authors.initials: SA
authors.lastname: Ali
authors.forename: Ludmila
authors.initials: L
authors.lastname: Velkova
authors.forename: Rumyana
authors.initials: R
authors.lastname: Hristova
authors.forename: Maria
authors.initials: M
authors.lastname: Angelova
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Voelter
authors.forename: Bart
authors.initials: B
authors.lastname: Devreese
authors.forename: Jozef
authors.initials: J
authors.lastname: Van Beeumen
authors.forename: Pavlina
authors.initials: P
authors.lastname: Dolashka-Angelova
mesh_terms: D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D020134:Catalytic Domain; D002942:Circular Dichroism; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics; D013696:Temperature
chemical_list: D007527:Isoenzymes; D013482:Superoxide Dismutase