4- A-acetyl

This enzyme [EC 2.4.1.16], also known as chitin-UDP N-acetylglucosaminyltransferase, catalyzes the reaction of UDP-A-acetyl-D-glucosamine with [(1,4)-(A-ace tyl-jS-D-glucosaminyl)] to produce UDP and [(l,4)-(A-acetyl-j8-D-glucosaminyl)]( +i). The enzyme ultimately converts UDP-A-acetyl-D-glucosamine into chitin and UDP. 

Figure 2 Proposed mechanism for acetyl phosphate hydrolysis by Gutsche s metallomi-celle 4 (a) acetyl transfer mechanism, (b) general base mechanism.

A 4-(A -acetyl-L-tyrosineazo)benzamidoethyl derivative of agarose has been synthesized and used for the selective immobilization of proteins. The azo bond of the derivative can be reduced to liberate 4-aminobenzamidoethyl-agarose, which can be diazotized and recoupled to A -acetyl-L-tyrosine and subsequently to a fresh preparation of protein. Regeneration successively through five cycles is possible without detectable loss of functional groups. 

Chitin forms the skeletal structure of invertebrates such as insects, spiders, crustaceans, etc. It is always found in conjunction with calcium carbonate and/ or proteins, and, chemically, it is a poly(i3-( 1 4)-A -acetyl-2-... 

Blackwell, J. 1969. Structure of P-chitin or parallel chain systems of poly-P-(l—>4)-A-acetyl-D-glucosamine. Biopolymers. 7 281-298. 

Polymer of p-(1 -4)-A/-acetyl-D-glucosamine units FIGURE 22.1 Structure of chitin and chitosan. 

A -Acetyl-3, 5 -0-(tetraisopropyldisiloxane-l,3-diyl)cytidine, T-38 iV-Acetyl-5-thio-D-glucosamine, A-349 iV-Acetylthomosamine, A-377 iV-Acetyl-2,3,4-tri-0-acetyl-D-ribosylamine, R-145 iV-Acetyl-2,3,4-tri-0-acetyl-D-xylosamine, X-88 A-Acetyl-2,3,4-tri-0-acetyl-L-xylosamine, X-88... 

On the other hand, chitin obtained from the carapace is a popular adsorbent [11] or a starting material for the production of adsorbing media like the amino-acid substituted glucans [12], and is insoluble in water and does not form a gel in water. Being different from the structure of alginic acid, chitin is poly-y8-(l,4)-A -acetyl-D-glucosamine. Three polymorphic forms have been identified by X-ray methods. Among a-, j8- and y-chitin, or-chitin appears to be the most stable form and consists of a series of sheets of twofold chains [13]. 

Chitin, poly(p-(l - 4)-A-acetyl-D-glucosamine), is widely distributed in nature, is one of the most abundant organic compounds on Earth and is of great importance in different fields since it possesses unique structures and characteristics different from typical synthetic polymers. Chitin is obtained from lower animals, mainly extracted from crustaceans. The structure of chitin is similar to cellulose, with acetamide groups at the C2 positions in place of hydroxyl (Scheme 12.2). 

Figure 9.4. A -acetyl-lactosamine family of A -linked oligosaccharides. 

A -Acetyl-Hydroxylation of Sialic Acids 4.4.1. Occurrence of A -GIycoIoylneuraminic Acid... 

Chitin (poly p-l-4-A/-acetyl-D-glucosamine) is one of the most abundant biopolymers on the planet. It is mainly found as a structural component of crustaceans and insects or in the cell wall of fungi. Chitosan (CHIT), a deacetylated form of chitin presents far greater solubility in aqueous acids than chitin due to its ability to be protonated to a polycation at low pH. Its ease of further modification, availability and low cost... 

---