Enzymatic Depolymerization

By enzymatic means, chitosan can be easily depolymerized by a variety of hydrolases including lysozyme, pectinase, cellulases, hemicellulases, lipases and amylases, among others, thus showing a peculiar vulnerability to enzymes other than chitosanases [71-76]. While pectinase is of particular... 

LMWHs are formed by various methods of fractionation or depolymerization of polymeric heparin (Table 7.1). Although they are enzymatically derived from UFH, they have a different site of achon and can be administered subcutaneously. LMWHs exert their anhcoagulant effect by inhibiting factor Xa and augmenting tissue-factor-pathway inhibitor, but minimally affect thrombin or factor Ila (Figs. 7.1 and 7.2)." Thus, the PTT, a measure of antithrombin (anh-factor Ila) achvity, is not used to measure the achvity of LMWHs. 

Aim of this work was to optimise enzymatic depolymerization of pectins to valuable oligomers using commercial mixtures of pectolytic enzymes. Results of experiments in continuous and batch reactor configurations are presented which give some preliminary indications helpful to process optimisation. The use of continuous reactors equipped with ultrafiltration membranes, which assure removal of the reaction products, allows to identify possible operation policy for the improvement of the reaction yield. 

The total activity of the enzymatic mixture was determined from the percentage reduction of viscosity [12] during the depolymerization of solutions, buffered at different pH values, containing 1 % (w/v) of the polygalacturonic acid or 0.5% (w/v) of pectin. A Cannon-Fenske viscosimeter, (ASTM series n° 150) kept at the constant temperature of 25 °C, was used to carry out the tests. 

Shoham Y, E Rosenberg (1983) Enzymatic depolymerization of emulsan. J Bacterial 156 161-167. 

The polyester domains of suberized walls can also be depolymerized using chemical and/or enzymatic approaches similar to those used for cutin. The aromatic domains are far more difficult to depolymerize as C-C and C-O-C crosslinks are probably present in such domains. Therefore, more drastic degradation procedures such as nitrobenzene, CuO oxidation, or thioglycolic... 

Figure 1.15 gives an overview of the main constituents of non food biomass. There are three components Cellulose, hemicellulose and lignin. Cellulose and hemicellulose are built form sugar-type monomers, but their cost-effective isolation through enzymatic depolymerization remains a challenge. 

II) complexes. This method was also successfully applied to chemically derivatized GAGs that cannot be depolymerized by enzymes [62]. Similarly, capillary electrophoresis (CE) can be used for digested GAGs that are then detected by ultraviolet spectroscopy or mass spectrometry. Complexation of GAGs using copper (II) ions improved the sensitivity. However, complete separation of intact GAGs was not feasible by CE and most methods still rely on enzymatic or chemical depolymerization prior to analysis [46]. 

Water is not just the solvent in which the chemical reactions of living cells occur it is very often a direct participant in those reactions. The formation of ATP from ADP and inorganic phosphate is an example of a condensation reaction in which the elements of water are eliminated (Fig. 2-22a). The reverse of this reaction— cleavage accompanied by the addition of the elements of water—is a hydrolysis reaction. Hydrolysis reactions are also responsible for the enzymatic depolymerization of proteins, carbohydrates, and nucleic acids. Hydrolysis reactions, catalyzed by enzymes called... 

It has been suggested that hydrogen peroxide and iron are the cause of this rapid depolymerization (30). It is possible that the initial attack by micro-organisms is not enzymatic but hydrolytic and oxidative in nature. If this is true, then a preservative system could be based on anti-oxidant properties of the chemical. If the initial attack can be stopped, then the total attack has been stopped. It is also possible that the initial and sustained attacks are caused by a combination of chemical... 

Muzzarelli RAA (1997) Human enzymatic activities related to the therapeutic administration of chitin derivatives. Cell Mol Life Sci 53 131-140 Muzzarelli RAA, Xia W, Tomasetti M and Ilari P (1995) Depolymerization of chitosan and substituted chitosans with the aid of a wheat germ lipase preparation. Enz Microbial Tech 17 541-545... 

E. K. Chernysheva (1972). A study of the metabolism of high-molecular polyphosphates, and their enzymatic depolymerization, in Neurospora crassa (in Russian). Candidate s Thesis, Moscow. Moscow State University. 

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