Table 4 Mode of action for enzymatic hydrolysis of cellulose by enzymes from various classes
From: Stochastic molecular model of enzymatic hydrolysis of cellulose for ethanol production
Enzyme class | Mode of action |
|---|---|
Endo-cellulase (EG, Non-processive with CBM) | • Carbohydrate binding module (CBM) binds to surface chains randomly and breaks bonds at catalytic domain (CD) |
Endo-cellulase (EG, Non-processive without CBM) | • Breaks bonds on surface chains in a random pattern |
Endo-cellulase (EG, Processive with CBM) | • CBM binds to surface chains randomly and break bond at CD |
|  | • Enzyme moves along the chain (towards non-reducing end or reducing end) and cuts every alternate bond releasing cellobiose until a minimum chain length is achieved |
Exo-cellulase (CBH I, Processive) | • CBM attaches from reducing end only on surface chains and pulls the chain towards CD |
|  | • Chain passes through CD (tunnel like shape) and every alternate bond is broken to produce cellobiose |
|  | • Enzyme moves along the chain (towards non-reducing end) and cut every alternate bond until a minimum chain length is reached |
Exo-cellulase (CBH I, Non-Processive) | • Attack from reducing end on surface chains and cuts every alternate bond to produce cellobiose |
Exo-cellulase (CBH II, Processive) | • CBM attaches from non-reducing end on surface chains and pulls the chain towards CD |
|  | • Chain passes through the tunnel shaped CD and every alternate bond is broken to produce cellobiose |
|  | • Enzyme moves along the chain (towards reducing end) and cuts every alternate bond until a minimum chain length is reached |
Exo-cellulase (CBH II, Non-Processive) | • Attack from non-reducing end on surface chains and breaks alternate bonds to produce cellobiose |
β-glucosidase | • Acts on cellobiose and soluble oligomers (DP ≤ 6) and produce glucose by breaking bond |