tailieunhanh - Báo cáo khoa học: Surface density of cellobiohydrolase on crystalline celluloses A critical parameter to evaluate enzymatic kinetics at a solid–liquid interface

The enzymatic kinetics of glycoside hydrolase family 7 cellobiohydrolase (Cel7A) towards highly crystalline celluloses at the solid–liquid interface was evaluated by applying the novel concept of surface density (q) of the enzyme, which is defined as the amount of adsorbed enzyme divided by the maximum amount of adsorbed enzyme. | ềFEBS Journal Surface density of cellobiohydrolase on crystalline celluloses A critical parameter to evaluate enzymatic kinetics at a solid-liquid interface Kiyohiko Igarashi Masahisa Wada Ritsuko Hori and Masahiro Samejima Department of Biomaterials Sciences Graduate Schoolof Agriculturaland Life Sciences The University of Tokyo Japan Keywords cellobiohydrolase cellobiose dehydrogenase crystalline cellulose glycoside hydrolase solid-liquid interface Correspondence M. Samejima Department of Biomaterials Sciences Graduate School of Agricultural and Life Sciences The University of Tokyo 1-1-1 Yayoi Bunkyo-ku Tokyo 113-8657 Japan Fax 81 3 58415273 Tel 81 3 58415255 E-mail amsam@ Received 3 April2006 revised 26 April 2006 accepted 2 May 2006 doi The enzymatic kinetics of glycoside hydrolase family 7 cellobiohydrolase Cel7A towards highly crystalline celluloses at the solid-liquid interface was evaluated by applying the novel concept of surface density p of the enzyme which is defined as the amount of adsorbed enzyme divided by the maximum amount of adsorbed enzyme. When the adsorption levels of Trichoderma viride Cel7A on cellulose Ia from Cladophora and cellulose Ip from Halocynthia were compared the maximum adsorption of the enzyme on cellulose Ip was times higher than that on cellulose Ia although the rate of cellobiose production from cellulose Ip was lower than that from cellulose Ia. This indicates that the specific activity k of Cel7A adsorbed on cellulose Ia is higher than that of Cel7A adsorbed on cellulose Ip. When k was plotted versus p a dramatic decrease of the specific activity was observed with the increase of surface density p-value suggesting that overcrowding of enzyme molecules on a cellulose surface lowers their activity. An apparent difference of the specific activity was observed between crystalline polymorphs . the specific activity for cellulose Ia was almost twice that for cellulose