Characterization of Chitinase from White-Rot Fungus Irpex lacteus NK-1.

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Citation abstract

Chitin is a cell wall structural component of many fungi and is important for mycelium growth. Therefore, enzymes like chitinase which break down chitin, are likely important in fungi during morphological changes. Irpex lacteus, a white-rot fungus isolated from wood-rotting fungi, produces several chitinases. Although it produces a range of chitinases, there are currently no characterization reports exploring them, despite the interest and body of published works evaluating carbohydrate degrading enzymes. In this study, Il Chi18C was cloned and recombinantly produced using Pichia pastoris as a host. Properties of purified Il Chi18C were determined, revealing an optimal pH of 5.0 and temperature of 50 °C when using p NP- N,N '-diacetyl-β-D-chitobioside ( p NP-(GlcNAc) 2 ) as a substrate. It is activated in the presence of metal ions such as Mg 2+, Ca 2+, and Mn 2+, but inhibited by DMSO, EtOH, and SDS. The Km and Vmax of Il Chi18C for this substrate are 3.48 mM and 5.46 µM min -1, respectively. Using p NP-(GlcNAc) 2 and chitin powder as substrates, Il Chi18C predominantly exhibited exo-type chitinase activity, releasing chitobiose from the non-reducing ends of chitin chains. It was also observed that this enzyme acts on the fruiting body of Flammulina velutipes, releasing chitobiose as the main product.