Fig. 1

Alginate and alginate lyase. A Structures of alginate. Alginates comprise β-d mannuronic acid (M) and α-l-guluronic acid (G), which are arranged in three block-types (MM, GG and MG/GM). In the alginate-producing bacteria Azotobacter and Pseudomonas, O-2 and/or O-3 of d-mannuronate is acetylated by mannuronan acetylases [15, 16]. B Catalytic mechanism of alginate lyase. The negative charge on the carboxylate anion can be neutralised by metal ions or amino acids. The Brønsted acid and base refer to associated amino acids in specific enzymes. C Structures of alginate lyases. Left panel, β-jelly roll, PL7 alginate lyase A1-II’ (PDB: 2ZAA) from Sphingomonas sp. A1; middle panel, (α/α)n toroid, PL5 alginate lyase A1-I (PDB: 1HV6) from Sphingomonas sp. A1 and PL39 alginate lyase Dp0100 from D. phaphyphila (PDB: 6JPN); right panel, β-helix fold, PL6 polyG-specific alginate lyase (PDB: 6A40) from V. splendidus