5.1.3.37 hepta(beta-(1->4)-D-mannuronate)acid poor substrate Azotobacter vinelandii ? - ? 433804 5.1.3.37 hexa(beta-(1->4)-D-mannuronate) poor substrate Azotobacter vinelandii ? - ? 433809 5.1.3.37 additional information alginates from Durvillea antarctica, Lessonia nigrescens, Laminaria hyperborea and a bacterial mannuronan are epimerized. The enzyme converts the M blocks into MGM sequences leaving the G-blocks intact Azotobacter vinelandii ? - ? 89 5.1.3.37 additional information enzyme exhibits a non-random mode of action when acting on mannuronan and alginates of various monomeric compositions. On average 10 residues are epimerised for each enzyme-substrate encounter. A hexameric oligomer is the minimum size to accommodate activity. For hexa-, hepta- and octameric substrates the third M residue from the nonreducing end is epimerised first Azotobacter vinelandii ? - ? 89 5.1.3.37 additional information epimerization reaction is detected only when acetyl groups are removed from the poly-D-mannuronate substrate, suggesting that AlgG epimerization activity in vivo may be sensitive to acetylation of the D-mannuronan residues Pseudomonas aeruginosa ? - ? 89 5.1.3.37 additional information isoform AlgE7 degrades M-rich alginates and a relatively G-rich alginate from the brown algae Macrocystis pyrifera most effectively, producing oligomers of 4 (mannuronan) to 7 units. The sequences cleaved are mainly G-MM and/or G-GM. G-moieties dominate at the reducing ends even when mannuronan is used as substrate, so the AlgE7 lyase/epimerase probably stimulates the lyase pathway, indicating a complex interplay between the two activities Azotobacter vinelandii ? - ? 89 5.1.3.37 additional information the enzyme either slides along the alginate chain during catalysis or recognizes a pre-existing G residue as a preferred substrate in its consecutive attacks Azotobacter vinelandii ? - ? 89 5.1.3.37 additional information the minimal substrate contains 9 monosaccharide residues. Tracts of adjacent guluronate residues are readily formed. The reaction reaches an apparent equilibrium when the guluronate composition of the polymer is 75% Pseudomonas aeruginosa ? - ? 89 5.1.3.37 additional information effect of ManC5-Es on alginate structures, overview. Alginate in brown algae is first formed as a polysaccharide chain containing mannuronic acid residues only. These are subsequently transformed by the ManC5-E into guluronic acid residues, generating distinct patterns arranged in regions of MM-, GG- and MG-blocks (beta-D-mannuronic acid (M) and alpha-L-guluronic acid (G) residues). Patterns containing large stretches of adjacent guluronic acid residues (GG-blocks) form structured interchain associations in the presence of Ca2+ ions. These interchain junctions have the so-called egg-box conformation and are responsible for the gelling properties of alginate and cell-wall strengthening Ectocarpus siliculosus ? - ? 89 5.1.3.37 additional information effect of ManC5-Es on alginate structures, overview. Alginate in brown algae is first formed as a polysaccharide chain containing mannuronic acid residues only. These are subsequently transformed by the ManC5-E into guluronic acid residues, generating distinct patterns arranged in regions of MM-, GG- and MG-blocks (beta-D-mannuronic acid (M) and alpha-L-guluronic acid (G) residues). Patterns containing large stretches of adjacent guluronic acid residues (GG-blocks) form structured interchain associations in the presence of Ca2+ ions. These interchain junctions have the socalled egg-box conformation and are responsible for the gelling properties of alginate and cell-wall strengthening Ectocarpus siliculosus ? - ? 89