Enzymatic degradation stabilities

At temperatures above Tm, chemical and enzymatic degradation of microbial exopolysaccharides is enhanced. The apparent enhanced stability of microbial exopolysaccharides in their ordered confirmation is thought to be due to the glycosidic bonds in the backbone of the polymer which raises the activation energy. This restricted movement would also restrict access of enzymes and chemicals to the backbone. 

Schldmann M, P Fischer, E Schmidt, H-J Knackmuss (1990b) Enzymatic formation, stability, and spontaneous reactions of 4-fluoromuconolactone, a metabolite of the bacterial degradation of 4-fluorobenzoate. J Bacterial 172 5119-5129. 

Many observations document that modifications of peptides by substitution with artificial amino acids or D-amino acids can often protect against enzymatic degradation. This is especially true when more than one modification is made. We begin here with two examples in which replacement of a single natural amino acid with an artificial one had a favorable impact on biological stability. Then, the influence of substitution with D-amino acids is described. Examples involving two or more modifications with artificial amino acids and D-amino acids combined are presented in the following section. 

Some of recent papers by Ratner et al. [63, 64] revealed that there are significant differences in the surface chemistry of Biomer lots. The surface of some lots was dominated by poly(diisopropylaminoethyl methacrylate) (DPAEMA or DIPAM), a high molecular weight UV stabilizer, which was absent from some older lots [65]. Ratner et al. carried out comparative studies on in vitro enzymatic and oxidative degradation of two lots of Biomer, BSU 001 and BSP 067. Lot BSU 001 contains both DPAEMA and an antioxidant, Santowhite powder, while BSP 067 contains only the antioxidant. It was found that DPAEMA retarded the enzymatic degradation process, but accelerated oxidative degradation. 

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