title: A peroxidase from Lepista irina cleaves beta,beta-carotene to flavor compounds.
abstract: Extracellular liquid of the edible fungus Lepista irina was found to effectively degrade beta,beta-carotene, beta-lonone, beta-cyclocitral, dihydroactinidiolide, and 2-hydroxy-2,6,6-trimethylcyclohexanone were formed as volatile breakdown products of beta,beta-carotene with mycelium-free culture supernatants, whereas beta-apo-10'-carotenal was identified as non-volatile degradation product. The key enzyme catalyzing the oxidative cleavage of beta,beta-carotene was purified with an overall yield of 63% and a purification factor of 43. Biochemical characterization showed a molecular mass of 50.5 kDa and an isoelectric point of 3.75. Fastest beta,beta-carotene degradation occurred at 34 degrees C and pH values between 3.5 and 4. Degenerate oligonucleotides were derived from N-terminal and internal amino acid sequences. By means of PCR-based cDNA-library screening a 1284 bp cDNA was identified which showed great overall similarity to Pleurotus eryngii polyvalent peroxidases. The obtained sequence contains an open reading frame of 1083 nucleotides, encoding a polypeptide of 361 amino acids. A 30 amino acid signal peptide was identified upstream of the N-terminal sequence of the mature enzyme. The L. irina versatile peroxidase represents the first microbial enzyme capable of carotenoid degradation that has been characterized on a molecular level, proving the participation of extracellular enzymes of white rot fungi in biotic carotenoid degradation processes.
authors.affiliation: Zentrum Angewandte Chemie, Institut für Lebensmittelchemie der Universität Hannover, Wunstorfer Strasse 14, D-30453 Hannover, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Zorn
authors.forename: Sabine
authors.initials: S
authors.lastname: Langhoff
authors.forename: Manuela
authors.initials: M
authors.lastname: Scheibner
authors.forename: Manfred
authors.initials: M
authors.lastname: Nimtz
authors.forename: Ralf G
authors.initials: RG
authors.lastname: Berger
mesh_terms: D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000201:enzymology*; D001673:Biodegradation, Environmental; D002338:Carotenoids / Q000737:chemistry; D003470:Culture Media; D005421:Flavoring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D045792:Norisoprenoids / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014835:Volatilization; D019207:beta Carotene / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005421:Flavoring Agents; D045792:Norisoprenoids; C427759:beta-apo-10'-carotenal; D019207:beta Carotene; D002338:Carotenoids; C008157:beta-ionone; D009195:Peroxidase