23 by: Benjamin Sinclair
Student – Benjamin Sinclair
My enzyme is cellulase, or more specifically endoglucanase (EG). Its EC number is 3.2.1.4. Endoglucanases are a form of cellulase which cleave the internal 1-4 beta glycosidic linkages of cellulose, reducing its degree of polymerization. They are involved in the total breakdown of cellulose along with other cellulase-type enzymes including exocellobiohydrolases, which act at the end of a shortened polymer strand to release glucose dimers, and beta 1-4 glucosidases, which break down disaccharides and oligosaccharides into glucose. Cellulases are most commonly found in microorganisms. Many microorganisms like bacteria, archaea and fungi produce cellulase as a group of enzymes and secrete them into the extracellular matrix to break down the cellulose of plants. The focus of this video is specifically endoglucanase EG-1 from the fungus Trichoderma reesei. The specific amino acid residues and their positions are from this enzyme specifically, but the active sites of all endoglucanases are extremely similar. All feature two residues of either aspartic or glutamic acid to carry out the acid/base catalyzed hydrolysis of glycosidic linkages. One of the residues has nucleophilic functionality while the other has proton transfer functionality. Other substrate binding residues are sometimes present in the active site but this one from T. reesei is stabilized only from H-bonds to the catalytic residues.
References
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