Polysaccharides biocatalysis

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Keywords Biocatalysis Enzymatic polymerization Polyester Polyisoprene Polysaccharide Transferase... 

Carbohydrates such as trioses, tetroses, pentoses, hexoses and polysaccharides are extremely important molecules in nature. The biological significance of oligosaccharides for cell-cell interaction is increasingly understood (Fukuda and Hindsgaul, 1994). The simple carbohydrates are the building blocks of oligo- and polysaccharides. Biocatalysis... 

Biocatalysis is a key route to both natural and non-natural polysaccharide structures. Research in this area is particularly rich and generally involves at least one of the following three synthetic approaches 1) isolated enzyme, 2) whole-cell, and 3) some combination of chemical and enzymatic catalysts (i.e. chemoenzymatic methods) (87-90). Two elegant examples that used cell-fi-ee enzymatic catalysts were described by Makino and Kobayashi (25) and van der Vlist and Loos (27). Indeed, for many years, Kobayashi has pioneered the use of glycosidic hydrolases as catalysts for polymerizations to prepare polysaccharides (88,91). In their paper, Makino and Kobayashi (25) made new monomers and synthesized unnatural hybrid polysaccharides with regio- and stereochemical-control. Van der Vlist and Loos (27) made use of tandem reactions catalyzed by two different enzymes in order to prepare branched amylose. One enzyme catalyzed the synthesis of linear structures (amylose) where the second enzyme introduced branches. In this way, artificial starch can be prepared with controlled quantities of branched regions. 

The synthesis of oligosaccharides and polysaccharides can also be achieved via microbial biocatalysis. For example, Wang et al (17) devised the Superbug method that could produce oligosaccharides of less than 4 sugar units efficiently. 

Enzymes from plants have been used since andent times, even though their nature remained obscure until the nineteenth century. Malting of cereals and the hydrolysis of complex polysaccharides are two of the oldest uses of enzymes in human history. Like their animal counterparts, most commerdally available plant-derived enzymes are hydrolases, particularly lipases and proteases. Papain, a cysteine protease from papaya, is the best-known plant-derived hydrolytic enzyme. Bromelain from pineapple and ficain from fig latex are similar cysteine proteases that have also found applications in biocatalysis. Horseradish peroxidase is a versatile oxidative enzyme obtained from its namesake that oxidizes many organic compounds, especially phenols. Hydroxynitrile lyase (often called oxynitrilase) from bitter almond is one of the most important plant-derived... 

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