Chitinase polysaccharides

Microbial polysaccharides have been shown to stress plant cells, resulting in elicitation (induction) and increased metabolite synthesis. Induction of various enzymes has been reported. Chitosan successfully elicited chitinase production in carrot (Daucus carota) cell cultures and elicitation of desired food ingredients and processing aids via chitosan has been attempted. 

As a result of the various acidic and enzymic degradative studies on chitin, there can be little doubt that the polysaccharide is a homogeneous polymer composed of 2-acetamido-2-deoxy-D-glucose residues. Moreover, the specificity of chitinases as 2-acetamido-2-deoxy-/3-D-glucosidases confirms the /3-d nature of the glycosidic linkages. 

Other Non-Catalytic Domains. Many polysaccharide depolymerizing enzymes are secreted by bacteria and fungi from their intracellular site of synthesis across the periplasmic space and cell wall into the surroundings. These exported enzymes reach their destination via the general secretory pathway [246] which involves membrane protein complexes such as the bacterial ABC transporters [247] that recognize domains on the secreted proteins. There are several examples of non-catalytic domains on microbial carbohydrases that may play a role in transport from the cells. These include a repeat domain on a chitinase involved... 

Chitin is the most abundant biomacromolecule in the animal field, which is found normally in invertebrates as a structural component. This important polysaccharide was synthesized for the first time by the enzymatic polymerization using chitinase and a chitobiose oxazoline derivative (Scheme 14).131 The latter activated monomer has a distorted structure with an a configuration at Cl, which resembles a transition-state structure of substrate chitin at the active site during a hydrolysis process (Scheme 15).3b 131132 The ring-opening polyaddition of the chitobiose oxazoline derivative was exclusively promoted by chitinase at pH 10.6, where the hydrolytic activity of chitinase was very much lowered. 

Although the specificity of the CBMs binding polysaccharides is the same as the catalytic domain more often than not, there are many examples to the contrary from enzymes hydrolysing the plant cell wall. Thus, an acetylxylan esterase Cellvibrio japonicus ioxm.Qx y P.fluorescens subsp. cellulosa) contains a cellulose binding domain. Moreover the modular structure permits fairly complicated proteins to be built up one chitinase, for example, from a hyperthermophilic archeon, had two GH 18 catalytic domains and two Family 1 and a Family 5 CBMs. °... 

Characterization data of the resulting cellulose-chitin hybrid polysaccharide 3 are summarized in Table 1. The average molecular wei t value (M ) of the resulting product 3 via cellulase- and chitinase catalyzed polymerization reached to 2840 and 4030, which correspond to 15-16 and 22 saccharide units, respectively. 

The yields and Mn value of the resulting chitin-chitosan hybrid polysaccharides 8 under various reaction conditions were summarized in Table 2. The yields of 8 were around 60-75% and there were little significant differences in catalysis between these two enzymes except for the reaction time. However, A4 value of 8 reached 1600 and 2020 with using chitinases from Bacillus sp. and Serratia marcescens, respectively, which correspond to 8-10 (n = 4-5) and 10-12 (n = 5-6) saccharide units, respectively. These results Indicated that values of polysaccharides are controllable to some extent by selecting enzymes from different origins. 

Chitinase from Bacillus sp. was added to a solution of Xyl (l— 4)GlcNAc oxazoline 13 dissolved into a phosphate buffer. The consumption rate of 13 was accelerated by the enzyme addition and chitin-xylan hybrid polysaccharide 14 was produced. During the polymerization, the reaction proceeded homogenously throughout the reaction. The yield was 76% and its average molecular weight value of 14 was M = 1500 with MJMa = 1.76, determined by GPC. Furthermore, MALDI-TOF mass spectrum of 14 indicated the peaks at every m/z 335, which corresponds to the molecular mass of the repeating disaccharide unit. 

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