Sandbox Reserved 655: Difference between revisions

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Cellulose is one of the main components of the plant cell wall, found predominantly in the xylem tissue which is further protected by hemicellulose and pectin. Cellulases are enzymes that catalyze the hydrolysis of cellulose and belong to a group of enzymes termed glycoside hydrolases (GHs). Several members of the GH family demonstrate a modular architecture composed of one or two catalytic modules connected to several kinds of accessory modules (Schubot et al., 2004). The accessory modules can be involved in numerous functions. For example, some cellulases contain carbohydrate-binding modules (CBMs), which enhance the association of the catalytic modules with insoluble carbohydrates. Cellulases have been characterized as endo or exo according to their mode of action on the substrate (Parsiegla et al., 2002). The endocellulases cleave the cellulose chain at arbitrary points, while exocellulases cleave at the terminus of a chain to start the degradation process. Beta-1,4-glycosidic bonds link together the beta-D-glucopyranose units of cellulose. Beta-1-4-endoglucanase enzymes, produced chiefly by fungi, bacteria and protozoans, specifically cleave the internal bonds of the cellulose chain (Kumar et al., 2008).

Cellulose is one of the main components of the plant cell wall, found predominantly in the xylem tissue which is further protected by hemicellulose and pectin. Cellulases are enzymes that catalyze the hydrolysis of cellulose and belong to a group of enzymes termed glycoside hydrolases (GHs). Several members of the GH family demonstrate a modular architecture composed of one or two catalytic modules connected to several kinds of accessory modules (Schubot et al., 2004). The accessory modules can be involved in numerous functions. For example, some cellulases contain carbohydrate-binding modules (CBMs), which enhance the association of the catalytic modules with insoluble carbohydrates. Cellulases have been characterized as endo or exo according to their mode of action on the substrate (Parsiegla et al., 2002). The endocellulases cleave the cellulose chain at arbitrary points, while exocellulases cleave at the terminus of a chain to start the degradation process. Beta-1,4-glycosidic bonds link together the beta-D-glucopyranose units of cellulose. Beta-1-4-endoglucanase enzymes, produced chiefly by fungi, bacteria and protozoans, specifically cleave the internal bonds of the cellulose chain (Kumar et al., 2008). Particularly interesting among this group of enzymes are the ones produced by thermophilic bacteria e.g. the beta -1,4-glucanase (EC 3.2.1.4)from Alicyclobacillus acidocaldarius (Aa_Cel9A), a thermoacidophilic Gram-positive bacterium, displays a temperature optimum of 343 K and a pH optimum of 5.5 (Eckert et al.,2002). Enzymes that can resist higher temperatures and a range of pHs are required since heat and/or chemical pretreatment processes are currently used to remove lignin to expose cellulose to cellulases (Sticklen, 2008)

[[Image:3vdh_bio_r_500.jpg | thumb]]

Sandbox Reserved 655: Difference between revisions

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 <Structure load='3vdh' size='500' frame='true' align='right' caption='Beta-1,4-Endoglucanase' scene='Insert optional scene name here' />
-Cellulose is one of the main components of the plant cell wall, found predominantly in the xylem tissue which is further protected by hemicellulose and pectin. Cellulases are enzymes that catalyze the hydrolysis of cellulose and belong to a group of enzymes termed glycoside hydrolases (GHs). Several members of the GH family demonstrate a modular architecture composed of one or two catalytic modules connected to several kinds of accessory modules (Schubot et al., 2004). The accessory modules can be involved in numerous functions. For example, some cellulases contain carbohydrate-binding modules (CBMs), which enhance the association of the catalytic modules with insoluble carbohydrates. Cellulases have been characterized as endo or exo according to their mode of action on the substrate (Parsiegla et al., 2002). The endocellulases cleave the cellulose chain at arbitrary points, while exocellulases cleave at the terminus of a chain to start the degradation process. Beta-1,4-glycosidic bonds link together the beta-D-glucopyranose units of cellulose. Beta-1-4-endoglucanase enzymes, produced chiefly by fungi, bacteria and protozoans, specifically cleave the internal bonds of the cellulose chain (Kumar et al., 2008).
+Cellulose is one of the main components of the plant cell wall, found predominantly in the xylem tissue which is further protected by hemicellulose and pectin. Cellulases are enzymes that catalyze the hydrolysis of cellulose and belong to a group of enzymes termed glycoside hydrolases (GHs). Several members of the GH family demonstrate a modular architecture composed of one or two catalytic modules connected to several kinds of accessory modules (Schubot et al., 2004). The accessory modules can be involved in numerous functions. For example, some cellulases contain carbohydrate-binding modules (CBMs), which enhance the association of the catalytic modules with insoluble carbohydrates. Cellulases have been characterized as endo or exo according to their mode of action on the substrate (Parsiegla et al., 2002). The endocellulases cleave the cellulose chain at arbitrary points, while exocellulases cleave at the terminus of a chain to start the degradation process. Beta-1,4-glycosidic bonds link together the beta-D-glucopyranose units of cellulose. Beta-1-4-endoglucanase enzymes, produced chiefly by fungi, bacteria and protozoans, specifically cleave the internal bonds of the cellulose chain (Kumar et al., 2008). Particularly interesting among this group of enzymes are the ones produced by thermophilic bacteria e.g. the beta -1,4-glucanase (EC 3.2.1.4)from Alicyclobacillus acidocaldarius (Aa_Cel9A), a thermoacidophilic Gram-positive bacterium, displays a temperature optimum of 343 K and a pH optimum of 5.5 (Eckert et al.,2002). Enzymes that can resist higher temperatures and a range of pHs are required since heat and/or chemical pretreatment processes are currently used to remove lignin to expose cellulose to cellulases (Sticklen, 2008)
 [[Image:3vdh_bio_r_500.jpg | thumb]]