Expression, purification, crystallization and X-ray diffraction analysis of ChiL, a chitinase from Chitiniphilus shinanonensis

Chitin, a linear polysaccharide consisting of β-1,4-linked N-acetyl-D-glucos­amine (GlcNAc), is widely used because of its biochemical properties. GlcNAc oligomers prepared from chitin have useful biological activities, such as immunostimulation and the induction of plant defence responses. Microbial chitinolytic enzymes have been investigated extensively for their potential use in the eco-friendly enzymatic production of GlcNAc and its oligomers. Chitini­philus shinanonensis SAY3^T is a recently found bacterium with a strong chitinolytic activity. The chitinolytic enzymes from this strain are potentially useful for the efficient production of GlcNAc and its oligomers from chitin. ChiL from C. shinanonensis is an endo-type chitinase belonging to the family 18 glycoside hydrolases (GH18). To understand the enzymatic reaction mechanism of ChiL and utilize it for further enzyme engineering, the catalytic domain (41–406) of ChiL, the construct for which was carefully designed, was expressed, purified and crystallized by the vapour-diffusion method. The crystal belonged to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 69.19, b = 81.55, c = 130.01 Å, and diffracted to 1.25 Å resolution. The Matthews coefficient (V_M = 2.2 ų Da⁻¹) suggested the presence of two monomers per asymmetric unit with a solvent content of 45%.