STUDIES OF CELLULOSE-BINDING BY CELLOBIOSE DEHYDROGENASE AND A COMPARISON WITH CELLOBIOHYDROLASE-1

The binding isotherm to cellulose of cellobiose dehydrogenase (CDH) fr om Phanerochaete chrysosporium has been compared with that of cellobio hydrolase 1 (CBH 1) from Trichoderma reesei. CDH binds more strongly b ut more sparsely to cellulose than does CBH 1. In a classical Scatchar d analysis, a better fit to a one-site binding model was obtained for CDH than for CBH 1. The binding of both enzymes decreased in the prese nce of ethylene glycol, increased in the presence of ammonium sulphate and was unaffected by sodium chloride. Attempts to localize the cellu lose-binding site on CDH have also been made by exposing enzymically d igested CDH to cellulose and isolating the cellulose-bound peptides. T he results suggest that the cellulose-binding site is located internal ly in the amino acid sequence of CDH.