A comparative study of two isoforms of laccase secreted by the "white-rot" fungus Rigidoporus lignosus, exhibiting significant structural and functional differences.
Two isoforms of laccase were obtained as the predominant phenol-oxidases in defined medium liquid cultures of the "white-rot" fungus Rigidoporus lignosus (R. lignosus). A characterization of the two laccases was made in terms of molecular mass, isoelectric point, metal content and N-terminal sequence. Furthermore, in order to gain information on the structural features related to the metal centers, a study of their geometric arrangement and their redox ability was made. It turned out that the two isoenzymes greatly differed with regard to pH stability, catalytic and copper centers features. It is proposed that all such differences are dependent on the amino acid sequences, which cause a distortion of the copper sites, thus accounting for the redox potential values and kinetic properties.
Bonomo
R P
RP
Dipartimento di Scienze Chimiche, Università di Catania, Italy. rbonomo@dipchi.unict.it
Boudet
A M
AM
Cozzolino
R
R
Rizzarelli
E
E
Santoro
A M
AM
Sterjiades
R
R
Zappalà
R
R
D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000201:enzymology* / Q000235:genetics; D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004795:Enzyme Stability; D007526:Isoelectric Point; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D042845:Laccase; D008670:Metals / Q000737:chemistry; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D007527:Isoenzymes; D008670:Metals; D003300:Copper; D010088:Oxidoreductases; D042845:Laccase