Article,
Mannuronan C-5-epimerases and their application for in vitro and in vivo design of new alginates useful in biotechnology.
Metab. Eng., 1 (3): 262-9 (1999)
Abstract
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.
Tags
- ;
- alginates/*chemistry/*metabolism
- azotobacter
- base
- biotechnology
- carbohydrate
- data
- design
- dna
- drug
- epimerases/genetics/*metabolism
- evolution,
- gov't
- magnetic
- molecular
- non-u.s.
- primers/genetics
- research
- resonance
- sequence
- spectroscopy
- support,
- vinelandii/enzymology/genetics
