Figure 2.

The lignin biosynthesis pathway. Colored dots represent the presence of a given enzyme in a specific taxonomic group. The abbreviations used for the enzyme are: phenylalanine ammonia-lyase; cinnamate 4-hydroxylase (C4H); 4-coumarate:CoA ligase (4CL); cinnamoyl-CoA reductase (CCR); cinnamyl alcohol dehydrogenase (CAD); peroxidase; and laccase (LAC). Question marks (?) signify that the enzyme responsible for the particular function or its substrate is still uncertain, or that the occurrence of a particular compound in a given taxonomic group is suspected but has not been proven. The figure was adapted from Reference [13,49,67].