The flexibility of His157 was investigated using molecular dynamics (MD) simulations of LPMO, in the monomeric form to avoid artifacts from crystal packing. The MD simulation starting from structure reported here (with His157 in the inward conformation) did not show any snapshots with the outward conformation at a 1 microsecond timescale. However, we also performed MD simulations based on a related LMPO (PDB ID = 5UFV, monomer A), which indicated that His161 (at equivalent position to His157) is able to freely interconvert between the inward and outward conformations at the microsecond timescale (more than 10 transitions between inward and outward conformations were observed in 1 microsecond MD simulation). Therefore, we hypothesized that His157 in our structure is possibly trapped in a conformation which makes it difficult to explore outward conformation at the microsecond timescale.