Mannuronan C-5-epimerases and their application for in vitro and in vivo design of new alginates useful in biotechnology.
The industrially important polysaccharide alginate is a linear copolymer of beta-D-mannuronic acid (M) and alpha-L-guluronic acid (G). It is produced commercially by extraction from brown seaweeds, although some of the bacteria belonging to the genera Azotobacter and Pseudomonas also synthesize alginates. Alginates are synthesized as mannuronan, and varying amounts of the M residues in the polymer are then epimerized to G residues by mannuronan C-5-epimerases. The gel-forming, water-binding, and immunogenic properties of the polymer are dependent on the relative amount and sequence distribution of M and G residues. A family of seven calcium-dependent, secreted epimerases (AlgE1-7) from Azotobacter vinelandii have now been characterized, and in this paper the properties of all these enzymes are described. AlgE4 introduces alternating M and G residues into its substrate, while the remaining six enzymes introduce a mixture of continuous stretches of G residues and alternating sequences. Two of the enzymes, AlgE1 and AlgE3, are composed of two catalytically active domains, each introducing different G residue sequence patterns in alginate. These results indicate that the enzymes can be used for production of alginates with specialized properties.
UNIGEN Center for Molecular Biology and Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway.
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D000464:Alginates / Q000737:chemistry* / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000201:enzymology / Q000235:genetics; D001483:Base Sequence; D001709:Biotechnology; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism*; D002240:Carbohydrate Sequence; D017931:DNA Primers / Q000235:genetics; D015195:Drug Design; D019143:Evolution, Molecular; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data
D000464:Alginates; D017931:DNA Primers; D002238:Carbohydrate Epimerases; C086519:mannuronan c-5-epimerase