Characterization of cellobiohydrolase from a newly isolated strain of Agaricus arvencis.

A highly efficient cellobiohydrolase (cellulose 1,4-β-cellobiosidase; CBH)-secreting basidiomycete, Agaricus arvensis KMJ623, was isolated and identified based on its morphological features and sequence analysis of internal transcribed spacer rDNA. Extracellular CBH was purified to homogeneity from A. arvencis culture supernatant using sequential chromatography and characterized. The relative mol. wt. of the purified CBH was determined to be 65 kDa by SDS-PAGE and 130 kDa by size-exclusion chromatography, indicating that the enzyme is a dimer. A. arvencis CBH showed a catalytic efficiency (kcat/Km) of 31.8 mM—1 s—1 using p-nitrophenyl-β-D-cellobioside as substrate, it is suggested that this is the highest value reported for a CBH-producing microorganism. The amino acid sequence of the enzyme showed significant homology with CBH from glycoside hydrolase family 7. It is concluded that although CBH have been purified and characterized from other sources, the A. arvencis CBH is distinguished from other CBH by its high catalytic efficiency.