AME prepress abstract  -  doi: 10.3354/ame01188

ABSTRACT: Extracellular peroxidases act on aromatic compounds such as humic substances resulting in the formation of unstable radicals. Most organisms known for the production of extracellular peroxidases populate terrestrial environments such as the wood-rotting fungus Phanerochaete chrysosporium or the Actinobacterium Streptomyces viridosporus. Only few studies focus on these enzymes acting in the aquatic environment. In this study, the activity of extracellular peroxidases in two distinct compartments of the artificially divided Lake Große Fuchskuhle (an acidic humic rich compartment and an almost neutral mesotrophic compartment) and in the catchment area was investigated. Additional, the effect of pH on extracellular peroxidase activity and the size fractions of water samples connected to the extracellular peroxidase activity were determined. The enzyme activity and the characterisation of the enzymes were essayed by oxidizing 2,2´-azino-di-(3-ethyl-benzthiazoline-6-sulphonic acid) (ABTS). In the humic rich compartment the activity of extracellular peroxidases was (except for one month) significantly higher as compared to the mesotrophic compartment with highest activities during fall and winter. In contrast, no peroxidase activity was detected in the catchment area. The pH optimum of extracellular peroxidases was at pH 3, and highest activity was detected in the molecular weight class of 10 kDa - 0.2 µm. The results document the occurrence of extracelluar peroxidases in Lake Große Fuchskuhle and suggest that these enzymes are involved in the degradation of aromatic compounds such as humic substances.