Figure 1.
Substrates used for assaying GE activity and compounds used as inhibitors for GE reactions. Esters of uronic acids used for assaying enzyme activity are shown: 1, BnzGlcA; 2, AllylGlcA; 3, MeGlcA; 4, MeGalA (A). The position of the OH group linked to the fourth carbon is equatorial for esters of GlcA and axial for GalA. The fourth position of GlcA is often methylated in native lignocellulose. R2 represents H in the model substrates but indicates the position where 4-O-MeGlcA is α-1,2–linked to the xylan backbone. The site of GE attack is indicated with an arrow. Hydroxycinnamic acids used as GE inhibitors are shown: 1, SA; 2, FA; 3, pCoA (B) and XUXXR (C). B and C compounds were added in increasing concentrations to enzymatic assays with BnzGlcA to investigate any inhibitory effect on GE activity with aromatic and carbohydrate compounds.