Cellular automata modeling depicts degradation of cellulosic material by a cellulase system with single-molecule resolution

Table 1 Enzyme kinetic parameters used in the CA model of cellulase action

CA model parameter
Enzyme	Type of cellulose material attacked	Type of chain cleavage	k ^a_cat [s⁻¹]	k ^b_off [s⁻¹]
CBH I	Crystalline	Exo	3.6^c	0.7 × 10^−3d
CBH II	Amorphous	Exo Endo	0.7^e 0.03	0.7 × 10^−2e –
EG	Amorphous	Endo	1.2^e	–

^aThe k _cat is the rate constant for polysaccharide cleavage in exo-mode, endo-mode, or both
^bThe k _off is the rate constant of chain dissociation for a cellobiohydrolase acting in processive chain cleavage mode; its reciprocal (1/k _off) is the time the cellobiohydrolase remains bound to the cellulose chain in such a mode of action event; an enzyme having k _off = 0 is perfectly processive, that is, it does not release the chain until it has reached its end. Therefore, in the case an obstacle is encountered during processive chain cleavage, this enzyme remains trapped until the obstacle is removed. Note that a cellobiohydrolase having k _off >0 is not an endoglucanase. It is an exo-acting enzyme that shows reduced processivity and is less likely to become trapped by obstacles to processive action
^cReference [16]
^dReference [46]
^eEstimated on comparing results of CA modeling to experimental data of AFM imaging

ISSN: 2731-3654