LACCASE AND THE DEPOSITION OF LIGNIN IN VASCULAR PLANTS

Laccase (p-diphenol:O-2 oxidoreductase, EC 1.10.3.2) was the first enzyme used to polymerize a synthetic lignin (DHP) in vitro. Based on that work, laccase was proposed to perform the same function in vivo. However, various biochemical and histological studies eventually led most researchers to believe that peroxidases, not laccases, were principally responsible for monolignol polymerization in vascular plants. Recent evidence from several laboratories necessitates a re-evaluation of the relative roles played by oxidases and peroxidases in lignin deposition. In this paper, we review the current literature regarding plant laccases, as well as selected fungal laccases. From this body of evidence, we have developed a model for the evolution of lignin as a structural polymer, and we describe how this model may be used to develop new questions regarding the origins of lignin and vascular plants.