Environmental control of lignin peroxidase, manganese peroxidase, and laccase activities in forest floor layers in humid Asia

We investigated the activities of ligninolytic enzymes, lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac), in forest floor layers collected from temperate and tropical regions in Japan, Thailand, and Indonesia. The effects of pH and Mn levels on the ligninolytic enzyme activities in the forest floor layers were analyzed. The activities of LiP, MnP, and Lac varied depending on the decomposition stage (i.e., depth) and pH of forest floor layers both in temperate and tropical regions. The activities of LiP, which has the lowest optimal pH, were higher in the highly acidic FH layers (pH < 5.0) than in the L layers. The activities of MnP and Lac were commonly detected in the less acidic L layers (pH > 5.0), whereas no MnP activity was detected in the highly acidic FH layers. These results indicate that MnP and LiP activities are dependent on pH and independent of the Mn concentrations in the forest floor layer. MnP and Lac play roles in the initial stage of litter decomposition, whereas acidification of forest floor layers enhances fungal activity and production of LiP in the FH layer.