Figure 1.

Schematics illustrating alginate block structures and general lyase mechanism of PL6 enzymes. A, 1,4-linked α-l-guluronic acid block (top), 1,4-β-d-mannuronic acid and α-l-guluronic acid mixed linkage block (middle), and 1,4-linked β-d-mannuronic acid block (bottom). n represents the continued polymer. B, syn-mechanism of alginate lyases with positions of catalytic Brøndsted acid (pink) and base (blue) and the uronic acid group neutralizer, ++ (typically Ca²⁺; in red).