Fig. 4

The β-elimination catalytic mechanism of PGLs. A. Mode of action in PGLs and PMGLs (X: –O–, the substrate is pectinate, X: –O–CH3, the substrate is pectin); B. Ca²⁺-assisted β-elimination catalytic mechanism; C. Common β-elimination catalytic mechanism in PGLs and PMGLs (Lys/Arg as catalytic base)