|Title (Primary)||First laccase in green algae: purification and characterization of an extracellular phenol oxidase from Tetracystis aeria|
|Author||Otto, B.; Schlosser, D.|
|Keywords||Laccase; Phenol oxidase; Algae; Dyes; Laccase-mediator system; Quaternary structure|
|UFZ wide themes||RU4;|
A green algal phenol oxidase was firstly purified, confirmed to be a laccase, and a hetero-oligomeric quaternary structure is suggested. The operation of a laccase-mediator system is firstly described in algae.
Laccases (EC 188.8.131.52) catalyze the oxidation of a multitude of aromatic substrates. They are well known in higher plants and fungi, while their presence in green algae appears uncertain. Extracellular laccase-like enzyme activity has previously been described in culture supernatants of the green soil alga Tetracystis aeria [Otto et al. in Arch Microbiol 192:759–768, (2010)]. As reported herein, the T. aeria enzyme was purified 120-fold by employing a combination of anion exchange and size exclusion chromatography. The purified enzyme was confirmed to be a laccase according to its substrate specificity. It oxidizes 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), syringaldazine, and 2,6-dimethoxyphenol (pH optima of pH ≤2.5, 7.0, and 6.5; K m values of 28.8, 40.5, and 1,830 µM; respectively), but not l-tyrosine or Fe2+. ABTS is by far the most efficient substrate. Two polypeptides, A (~110 kDa) and B (71 kDa), were co-purified by the applied procedure, both being highly N-glycosylated (≥~53 and ≥27 %, respectively). As suggested by various gel electrophoretic analyses, the native enzyme (apparent molecular mass of ~220 kDa) most probably is a hetero-oligomer with the composition AB 2 , wherein A is the catalytic subunit and B forms a disulfide-linked homo-dimer B 2 . The decolorization of anthraquinone (Acid Blue 62 and Remazol Brilliant Blue R) and diazo dyes (Reactive Black 5) was studied in the presence of redox-mediating compounds (ABTS and syringaldehyde), demonstrating the operation of the laccase-mediator system in algae for the first time. Thus, laccases from green algae may participate in the biotransformation of a wide spectrum of natural and xenobiotic compounds.
|Persistent UFZ Identifier||https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=15530|
|Otto, B., Schlosser, D. (2014):
First laccase in green algae: purification and characterization of an extracellular phenol oxidase from Tetracystis aeria
Planta 240 (6), 1225 - 1236