THE BEHAVIOR OF PHANEROCHAETE-CHRYSOSPORIUM CELLOBIOSE DEHYDROGENASE ON ADSORPTION TO CRYSTALLINE AND AMORPHOUS CELLULOSES

The adsorption of cellobiose dehydrogenase (CDH) to cellulose has been previously reported, However, the structural type of cellulose on to which CDH is adsorbed has not been investigated, In the present study we have compared the behaviour of CDH when it adsorbs on the highly cr ystalline cellulose microfibrils from Valonia macrophysa and on the co mpletely amorphous cellulose prepared from a solution of Avicel in the SO2/amine system. The isotherms of CDH adsorption to both Valonia and amorphous celluloses fit well with the Langmuir adsorption theory, Ho wever, the maximum adsorption of CDH to the amorphous cellulose was mu ch higher than that to Valonia cellulose, The location of CDH adsorbed on cellulose was revealed with colloidal-gold-tagged antibodies by tr ansmission electron microscopy. By using this technique it was demonst rated that CDH adsorption to Valonia cellulose was limited to the amor phous regions attached to the crystalline microfibrils, whereas no CDH was adsorbed to the surface of the highly crystalline microfibrils, F urthermore, continuous monitoring of cellulase activity showed that li mited amounts of structures susceptible to enzymic hydrolysis exist ev en on the surface of Valonia cellulose, From these observations, we co nclude that amorphous regions of cellulose seem to the preferred sites of CDH adsorption, whereas CDH is not adsorbed to the surface of high ly crystalline microfibrils.