4.2. Processivity
Processivity or multiple attack is a characteristic property of several
enzymes acting on polymer substrates, but there is still limited information
about the processivity of carbohydrate active enzymes. The most
studied processive carbohydrate active enzymes are cellulases and
chitinases,which hydrolyze non-soluble substrates [20,21]. Processivity
or multiple attack can be characterized with degree of multiple attack
(DMA), i.e., the number of bonds broken during the lifetime of an enzyme–
substrate complex minus one, but this definition is not suitable
for calculation. The other definition, i.e. ratio of the rates of formation
of oligomer and polymer products [22] allows the calculations only for
polymeric (insoluble) substrates. The phenomenon was studied in details
in case of nucleic acid motor enzymes and a mathematical formula
was suggested to determine the key parameters for processivity [16].
This relationship (see Eq. ()) was used to calculate our results summarized
in Table 1.
The mean number of steps increase with DP of substrate, the relationship
is quasi-linear and the x-axis intercept showed the size of
substrate without processivity. The highest value was 3.34 measured
on substrate of DP 11, which is in a good agreement with values 3.3
found earlier for amylose with average DP 44 [23].