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( Keisuke Kojima ),( Naoki Sunagawa ),( Kiyohiko Igarashi ),( Paul Dupree ) 한국목재공학회 2021 한국목재공학회 학술발표논문집 Vol.2021 No.1
Xylan is the major hemicellulose. The main chain is consisted of xylose residues, whereas the side chain differs by the plant species. For instance, xylan from hardwood is substituted by glucuronic acid and acetylated. In nature, fungi degrade xylan, producing various enzymes. In general, xylan main chain is degraded into xylooligosaccharides by xylanase. Thus, its substrate recognition is a crucial for the efficient digestion of xylan. Ample studies have reported about xyalanases’ substrate specificities towards xylan and xylooligosaccharides substituted with glucuronic acid. On the other hand, little is known about the effect of acetylation due to difficulty in extracting acetylated xylan. The basidiomycetes Phanerochaete chrysosporioum is a model organism for white rot fungi. P.c degrades hardwood in nature and has various enzymes. P.c has three xylanases belonging to GH family 10 and 11. In general, wood decay fungi have GH family 10 xylanases and mold has GH family 11 xylanases. Therefore, this study prepared substrates, investigated the reaction property of two xylanases from the P.c and compared GH family 10 and 11 xylanases’ characteristics. Finally, we proposed xylan degradation system using each xylanase.
Nakamura, Akihiko,Watanabe, Hiroki,Ishida, Takuya,Uchihashi, Takayuki,Wada, Masahisa,Ando, Toshio,Igarashi, Kiyohiko,Samejima, Masahiro American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.12
<P>Analysis of heterogeneous catalysis at an interface is difficult because of the variety of reaction sites and the difficulty of observing the reaction. Enzymatic hydrolysis of cellulose by cellulases is a typical heterogeneous reaction at a solid/liquid interface, and a key parameter of such reactions on polymeric substrates is the processivity, i.e., the number of catalytic cycles that can occur without detachment of the enzyme from the substrate. In this study, we evaluated the reactions of three closely related glycoside hydrolase family 7 cellobiohydrolases from filamentous fungi at the molecular level by means of high-speed atomic force microscopy to investigate the structure–function relationship of the cellobiohydrolases on crystalline cellulose. We found that high moving velocity of enzyme molecules on the surface is associated with a high dissociation rate constant from the substrate, which means weak interaction between enzyme and substrate. Moreover, higher values of processivity were associated with more loop regions covering the subsite cleft, which may imply higher binding affinity. Loop regions covering the subsites result in stronger interaction, which decreases the velocity but increases the processivity. These results indicate that there is a trade-off between processivity and hydrolytic velocity among processive cellulases.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-12/ja4119994/production/images/medium/ja-2013-119994_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja4119994'>ACS Electronic Supporting Info</A></P>