Chitin deacetylase

The most important derivative of chitin is chitosan obtained by partial deacetylation of chitin in the solid state under alkaline conditions or by enzymatic hydrolysis in the presence of a chitin deacetylase. The ratio of 2-acetamido-2-deoxy-D-glucopyranose to 2-amino-2-deoxy-D-glucopyra-nose moieties determines the identity of the product, that is, chitin or chitosan [9]. The published methods used for the production of chitosan from chitin are summarized in Table 2.3. 

Enzymatic hydrolysis is a useful method for the preparation of monomers from chitin and chitosan because the yield of monomers is greater by enzymatic hydrolysis than by acid hydrolysis. The enzyme chitin deacetylase hydrolyzes the acetamido group in the N-acetylglucosamine units of chitin and chitosan, thus generating glucosamine imits and acetic acid (Fig. 2.5). 

Chitin is a stable compoimd, incompatible with oxidizing agents [59]. In the solid state imder alkaline condition (e.g., NaOH, KOH, heat at about 120 °C) or by enzymatic hydrolysis in the presence of a chitin deacetylase, it hydrolyses to form the deacetylated degradation product chitosan [6,7,10,11]. It was found that the presence of urea in basic media and at low temperature (—20 °C) had little effect on chitin structure and that urea is of benefit to the stability of chitin solution [38]. 

In acidic condition including acetolysis with acetic anhydride/H2SO4, hydrolysis with HCl /sonolyses imder ultrasoimd irradiation, and fluor-ohydrolysis with anhydrous HF or by the enzyme chitin deacetylase, it forms smaller oligosaccharides [12]. 

Win and Stevens (2001) studied shrimp chitin as a substrate for chitin deacetylase for fungus Absidia coerulea. The chitin was exposed to physical and chemical treatment to obtain a better accessibility of its acetyl groups for deacetylation process. Chitin was exposed to physical treatments such as heating, sonicating, and grinding. None of these treatments increased the enzymatic deacetylation efficiency. 

Tsigos, I., Martinou, A., Kafetzopoulos, D., and Bouriotis, V. 2000. Chitin deacetylases New versatile tools in biotechnology. Tibtechnology 18, 305-312. 

Win, N.N. and Stevens, W.F. 2001. Shrimp chitin as substrate for fungal chitin deacetylase. Appl. Microbiol. Biotechnol. 57, 334—341. 

The most important chitin derivative is chitosan, obtained by its partial deacetylation under alkaline conditions or by enzymatic hydrolysis in the presence of chitin deacetylase. Because of the semicrystalline morphology of chitin, chitosan obtained by a solid-state reaction has a heterogeneous distribution of acetyl groups along the chain. On the other hand when chitin is treated with concentrated aqueous sodium hydroxide, N-deacetylation proceeds smoothly and homogeneously deacetylated samples are obtained [37]. 

Davis LL, Bartnicki-Garcia S (1984) Chitosan synthesis by the tandem action of chitin synthetase and chitin deacetylase from Mucor rouxii. Biochemistry 23 1065-1073... 

Chitin deacetylase has been used in the synthesis of partially and fully N-deacetylated 4-methyl umberlliferyl chitobiose derivatives as fluorogenic substrates for chitinase. Conversely, the reverse acylating action of chitin deacetylase has been used to prepare a partially N-acetylated chitosamine tetramer. The preparation of a 4-0-acetyl sialic acid derivative by a lipase OF-catalysed deacetylation of the peracetylated precursor has been reported. ... 

Septate- junction-dependent luminal deposition of chitin deacetylases restricts tube elongation in the Drosophila trachea. Current Biology 16,180-185. 

Chitin deacetylase from Colletotrichum lindemuthiamm, Mucor rouxii, Abisidia butleri, or Aspergillus nidulans may convert chitin from shell waste to chitosan (Kauss and Bauch 1988, Arcidiacono et al. 1989, Tsai et al. 2002). However, different preparation methods result in different DD, distribution of acetyl groups, chain length, and conformational structures (Rudrapatnam et al. 2002, Kurita 2006, Synowiecki 2007). 

Kauss, H. and Banch, B. 1988. Chitin deacetylase from CoUetotrichwn lindemuthianum. Methods Enzymol. 161 518-523. 

Kafetzopoulos, D., Martinou, A., and V. Bouriotis. 1993. Bioconversion of chitin to chitosan Purification and characterization of chitin deacetylase from Mucor rouxii. Proceedings of the National Academy of Sciences 90 2564-2568. 

Hekmat, O., K. Tokuyasu, and S. G. Withers. 2003. Subsite structure of the endo-type chitin deacetylase from a Deuteromycete, Colletotrichum lindemuthianum An investigation using steady-state kinetic analysis and MS. Biochem. J. 374 369-380. 

Industrial production of chitosan from chitin is usually carried out by high concentration of NaOH at high tanperatures. Alternatively, the conversion from chitin to chitosan can be achieved by chitin deacetylase (CDA, E.C.3.5.1.41). CDA is one of the monbers of the carbohydrate esterase... 

Martinou, A., Bouriotis, V., Stokke, B. T., and Varum, K. M. 1998. Mode of action of chitin deacetylase from Mucor mwcii on partially V-acetylated chitosans. Carbohydr Res 311 71-78. 

Tokuyasu, K., Mitsutomi, M., Yamaguchi, L, Hayashi, K., and Mori, Y. 2000a. Recognition of chitooligosac-charides and their V-acetyl gronps by putative subsites of chitin deacetylase from a Deuteromycete, Colletotrichum lindemuthianum. Biochemistry 39 8837-8843. 

Tokuyasu, K., Ono, H., Hayashi, K., and Mori, Y. 1999. Reverse hydrolysis reaction of chitin deacetylase and enzymatic synthesis of P-D-GlcNAc-(l-4)-GlcN from chitobiose. Carbohydr Res 322 26-31. 

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