Effect of substituent site on Polysaccharide Enzymatic Degradation
The importance of substituent site on polysaccharide degradability was demonstrated (Roesser et al., 1996). This work showed that by careful control of polysaccharide substitution site, modified polysaccharides can be obtained that are either more resistant, or increasingly susceptible, to enzymatic degradation. For a series of α-amylases, biodegradation of water soluble acetyl amylose proceeds at faster rates and to greater percent when acetylation of the polymer is at secondary 2-O/3-O as opposed to primary 6-O hydroxyl functionalities. Interestingly, these results were obtained using α-amylase enzymes from two distinct families (Bacillus and Fungi). The observed differences in rate as a function of substitution site must be due to changes in enzyme−substrate binding (Km) constants and/or maximum velocity (vmax) values.
Figure 28. Percent degradation as a function of time for (6-O)- and (2-O/3-O)-acetyl amylose polymers exposed to the α-amylase from A. oryzae.
- David S. Roesser, Stephen P. McCarthy, Richard A. Gross and David L. Kaplan, "Effects of Substitution Site on Acetyl Amylose Biodegradability by Amylase Enzymes", Macromolecules, Vol. 29, No. 1, 1-9 (1996).(PDF)