An exo β-1,3-glucanase synthesized de novo degrades lentinan during storage of Lentinule edodes and diminishes immunomodulating activity of the mushroom

Two β-1,3-glucanase isoenzymes, GNase I and II, were isolated from Lentinule edodes fruiting body. They degraded lentinan in an exo manner during storage of the mushroom. GNase I and II were monomeric proteins with apparent molecular masses of 72.9 and 74.7 kDa, respectively. It was shown that Km values for GNase I and GNase II against lentinan were 1.02 and 2.41 μM, respectively. Moreover, it was demonstrated by western blotting analysis that this enzyme was synthesized de novo in L. edodes during storage at 20 °C, but not at 1 or 5 °C. And this pattern of western blot was consistent with that of glucanase activity during storage of L. edodes. In addition, the immunomodulating effects of lentinan on TNF-α and NO production were diminished with its degradation by this enzyme. These results suggested that synthesis of exo β-1,3-glucanases were induced under storage conditions at 20 °C, and lentinan degradation by their attack might result in the depletion of immunomodulating activity of L. edodes.