Enzyme catalysis polysaccharide polymerization

A more specific catalysis was developed using enzymes as catalysts for polymerizations ( enzymatic polymerization ) starting in the mid-1980s, which can now be regarded as a third stream of polymerization catalyst. Normally, monomers of enzymatic polymerization are to be recognized and activated by the enzyme for the polymerization to occur, and thus polymers with precisely controlled structiues are expected. This articles concentrates on in vitro polysaccharide synthesis via enzymatic polymerization. 

Enzymes are generally classified into six groups. Table 1 shows typical polymers produced with catalysis by respective enzymes. The target macromolecules for the enzymatic polymerization have been polysaccharides, poly(amino acid)s, polyesters, polycarbonates, phenolic polymers, poly(aniline)s, vinyl polymers, etc. In the standpoint of potential industrial applications, this chapter deals with recent topics on enzymatic synthesis of polyesters and phenolic polymers by using enzymes as catalyst. 

Enzymes may be classified generally into six groups the details of typical polymers produced via catalysis with respective enzymes are listed in Table 23.1. In the past, the target macromolecules for enzymatic polymerization have included polysaccharides, poly(amino acid)s, polyesters, polycarbonates, phenolic polymers, poly(aniline)s, and vinyl polymers. In this chapter, attention is focused on the enzymatic synthesis of phenohc polymers and polyesters, based on the increasing industrial application of these materials. Notably, most such polymers can be obtained from commercially available, inexpensive monomers by using industrially produced enzymes. Another important point is that the enzymatic process must be regarded as an environmentally benign synthetic pathway. Details of the enzymatic synthesis of other polymers are provided in recent pertinent reviews [3-10]. 

For the polysaccharide synthesis, enzymatic polymerization has been developed as a new in vitro synthesis method of natural and unnatural polysaccharides having complicated structures.The method utilizes a hydrolysis enzyme to catalyze the bond formation for the polymer construction, a reverse direction of the hydrolysis to cleave the bond. This catalysis is due to the enzymatic characteristics, where enzymes catalyze the reverse reaction involving a common intermediate in both forward and backward reactions. In nature, there are many polysaccharides having N-acetyl groups called mucopolysaccharides such as chitin, hyaluronic acid (HA), and chondroitin (Ch). 

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