Structure and function characterisation of a bacterial copper dependent mono-oxygenase from C. cellulovorans, with particular insight into biofuel production.

Lytic polysaccharide mono-oxygenases (LPMOs) are a recently discovered, and rapidly expanding, family of enzymes capable of oxidizing complex polysaccharide polymers. They are attracting interest in biotechnology as potential factors in the efficient treatment of recalcitrant biomass with a particular focus on biofuel production. Previous work has identified key physiological features in LPMOs that are archetypal in the activity of these enzymes. Here we report that an enzyme from Caldibacillus cellulovorans(C. cellulovorans) with high sequence conservation with other LPMOs, displays high affinity copper binding characteristics typical of a CBM33 molecule. By using EPR, the active site of C. cellulovorans CBM33 is revealed as an axial type 2 copper centre in a histidine brace conformation, emblematic of the LMPO clan. Oxidative degradation of chitin and cellulose was proven with mass spectrometry studies, product identity suggested a propensity for C1 oxidation; however, potential C4 site oxidation by-products were observed. The broad spectrum activity of C. cellulovorans CBM33 could potentially stimulate a more diverse selection of efficient biofuel treatments. Further to this, oxidative activity at 80°C creates a new paradigm for high temperature biotechnology treatments for the degradation of recalcitrant polysaccharides.