title: Alginate sequencing: an analysis of block distribution in alginates using specific alginate degrading enzymes.
abstract: Distribution and proportion of β-D-mannuronic and α-L-guluronic acid in alginates are important for understanding the chemical-physical properties of the polymer. The present state of art methods, which is based on NMR, provides a statistical description of alginates. In this work, a method was developed that also gives information of the distribution of block lengths of each of the three block types (M, G, and MG blocks). This was achieved using a combination of alginate lyases with different substrate specificities, including a novel lyase that specifically cleaves diguluronic acid linkages. Reaction products and isolated fragments of alginates degraded with these lyases were subsequently analyzed with (1)H NMR, HPAEC-PAD, and SEC-MALLS. The method was applied on three seaweed alginates with large differences in sequence parameters (F(G) = 0.32 to 0.67). All samples contained considerable amounts of extremely long G blocks (DP > 100). The finding of long M blocks (DP ≥ 90) suggests that also algal epimerases act by a multiple attack mechanism. Alternating sequences (MG-blocks) were found to be much shorter than the other block types. In connection with method development, an oligomer library comprising both saturated and unsaturated oligomers of various composition and DP 2-15 was made.
authors.affiliation: Department of Biotechnology, Norwegian University of Science and Technology, NTNU Sem Sælands vei 6-8, N-7491 Trondheim, Norway. olava@nt.ntnu.no
authors.forename: Olav Andreas
authors.initials: OA
authors.lastname: Aarstad
authors.forename: Anne
authors.initials: A
authors.lastname: Tøndervik
authors.forename: Håvard
authors.initials: H
authors.lastname: Sletta
authors.forename: Gudmund
authors.initials: G
authors.lastname: Skjåk-Bræk
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D019757:Carbon-Oxygen Lyases / Q000737:chemistry*; D017421:Sequence Analysis / Q000379:methods*
chemical_list: D000464:Alginates; D019757:Carbon-Oxygen Lyases