Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Review Article
Publication Acceptance Date: May 5, 2008
Publication Date: May 1, 2009
Citation: Wong, D. 2009. Structure and Action Mechanism of Ligninolytic Enzymes. Applied Biochemistry and Biotechnology. 157(2):174-209. Technical Abstract: Lignin is the most abundant renewable source of aromatic polymer in nature, and its decomposition is indispensable for carbon recycling. It is chemically recalcitrant to breakdown by most organisms because of the complex, heterogeneous structure. The white-rot fungi produce an array of extracellular oxidative enzymes that synergistically and efficiently degrade lignin. The major groups of ligninolytic enzymes include lignin peroxidases, manganese peroxidases, and laccases. The two peroxidases are heme-containing enzymes with catalytic cycles that involve the formation and reduction of compound I and compound II intermediates. LiP has the unique ability to catalyze oxidative cleavage of C-C bonds and ether (C-O-C) bonds in non-phenolic aromatic substrates of high redox potential. MnP oxidizes Mn(II) to Mn(III), which facilitates the degradation of phenolic compounds or in turn oxidizes a second mediator for the breakdown of non-phenolic compounds. Laccases are multi-copper-containing proteins that catalyze the oxidation of reducing substrates with concomitant reduction of molecular oxygen to water. This review covers the chemical nature of lignin substrates, and focuses on the biochemical properties, molecular structures, reaction mechanisms, and related structures/functions of these enzymes.