title: Copper induction and differential expression of laccase in Aspergillus flavus.
abstract: Aspergillus flavus was isolated from soil and exhibited laccase activity under both constitutive and copper induced conditions. Spiking the medium with 1 mM copper sulfate resulted in an increase in the activity which reached 51.84 U/mL, a distinctive protein band was detected at 60 kDa. The extracellular enzyme was purified 81 fold using gel filtration chromatography and resulted in two different laccase fractions L1 and L2, the latter had a higher enzymatic activity which reached 79.57 U/mL and specific activity of 64.17 U/μg protein. The analysis of the spectrum of the L2 fraction showed a shoulder at 330 nm which is characteristic for T2/T3 copper centers; both copper and zinc were detected suggesting that this is an unconventional white laccase. Primers of laccase gene were designed and synthesized to recover specific gene from A. flavus . Sequence analysis indicated putative laccase (Genbank ID: JF683612) at the amino acid level suggesting a close identity to laccases from other genera containing the copper binding site. Decolorization of textile waste water under different conditions showed possible application in bioremediation within a short period of time. The effect of copper on A. flavus was concentration dependent.
authors.affiliation: Microbiology Department, National Center for Radiation Research and Technology, Cairo, Egypt.
authors.forename: Ola M
authors.initials: OM
authors.lastname: Gomaa
authors.affiliation: Agriculture Genetic Engineering Research Institute, Agriculture Research Center, Giza, Egypt.
authors.forename: Osama A
authors.initials: OA
authors.lastname: Momtaz
mesh_terms: D001231:Aspergillus flavus / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D002850:Chromatography, Gel; D003300:Copper / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004271:DNA, Fungal / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007220:Industrial Waste; D042845:Laccase / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012988:Soil Microbiology; D013057:Spectrum Analysis; D015533:Transcriptional Activation / Q000187:drug effects*; D018508:Water Purification
chemical_list: D003470:Culture Media; D004271:DNA, Fungal; D007220:Industrial Waste; D003300:Copper; D042845:Laccase
keywords: Aspergillus flavus; copper induction; laccase; textile waste water decolorization