Document Detail

Identification of nitrogen mineralization enzymes, L-amino acid oxidases, from the ectomycorrhizal fungi Hebeloma spp. and Laccaria bicolor.
MedLine Citation:
PMID:  18675352     Owner:  NLM     Status:  MEDLINE    
Amino acids are major nitrogen sources in soils and they harbour a central position in the nitrogen metabolism of cells. We determined whether Hebeloma spp. and Laccaria bicolor expressed the enzyme L-amino acid oxidase (LAO), which catalyses the oxidative deamination of the alpha-amino group of L-amino acids. We measured LAO activities from the mycelial extracts of seven laboratory-grown fungal strains with three methods, and we measured how LAO activities were expressed in one Hebeloma sp. strain grown on four nitrogen sources. Hebeloma spp. and L. bicolor converted L-phenylalanine, but not D-phenylalanine, to hydrogen peroxide, 2-oxoacid, and ammonia, suggesting that they expressed LAO enzymes. The enzymes utilized five out of seven tested L-amino acids as substrates. LAO activities were maximal at pH 8, where Michaelis constant (Km) values were 2-5mm. The LAO of Hebeloma sp. was expressed on every nitrogen source analysed, and the activities were the highest in mycelia grown in nitrogen-rich conditions. We suggest that LAO is a mechanism for cellular amino acid catabolism in Hebeloma spp. and L. bicolor. Many soil bacteria and fungi also express LAO enzymes that have broad substrate specificities. Therefore, LAO is a potential candidate for a mechanism that catalyses nitrogen mineralization from amino acids at the ecosystem level.
Jaro T Nuutinen; Sari Timonen
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-07-15
Journal Detail:
Title:  Mycological research     Volume:  112     ISSN:  0953-7562     ISO Abbreviation:  Mycol. Res.     Publication Date:  2008 Dec 
Date Detail:
Created Date:  2008-12-01     Completed Date:  2009-02-19     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8913481     Medline TA:  Mycol Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  1453-64     Citation Subset:  IM    
University of Helsinki, Department of Applied Biology, P.O. Box 27, FI-00014 University of Helsinki, Finland.
Data Bank Information
Bank Name/Acc. No.:
GENBANK/EF564167;  EF564168;  EF564169;  EF564170;  EF564171;  EF564172
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MeSH Terms
Base Sequence
DNA, Fungal / chemistry,  genetics
DNA, Intergenic / chemistry,  genetics
Hebeloma / enzymology*,  genetics
Hydrogen Peroxide / metabolism
Keto Acids / metabolism
L-Amino Acid Oxidase / genetics,  isolation & purification*,  metabolism
Laccaria / enzymology*,  genetics
Molecular Sequence Data
Mycelium / enzymology,  genetics
Mycorrhizae / enzymology*,  genetics
Quaternary Ammonium Compounds / metabolism
Reg. No./Substance:
0/DNA, Fungal; 0/DNA, Intergenic; 0/Keto Acids; 0/Quaternary Ammonium Compounds; 7722-84-1/Hydrogen Peroxide; EC Acid Oxidase

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