Extracellular laccases and peroxidases from sycamore maple (Acer pseudoplatanus) cell-suspension cultures

Abstract

Abstract.We have investigated the abilities of extracellular enzymes from dark-grown cell-suspension cultures of sycamore maple (Acer pseudoplatanus L.) to oxidize monolignols, the precursors for lignin biosynthesis in plants, as well as a variety of other lignin-related compounds. Laccase and peroxidase both exist as a multiplicity of isoenzymes in filtrates of spent culture medium, but their abilities to produce water-insoluble, dehydrogenation polymers (DHPs) from the monolignols (in the presence of hydrogen peroxide for the peroxidase reaction) appear identical whether or not the enzymes are purified from the concentrated filtrates or left in a crude mixture. The patterns of bonds formed in these DHPs are identical to those found in DHPs synthesized using horseradish peroxidase or fungal laccase, and many of these bonds are found in the natural lignins extracted from different plant sources. On the other hand, sycamore maple laccase is very much less active on phenolic substrates containing multiple aromatic rings than is sycamore maple peroxidase. We suggst that whereas laccase may function during the early stages of lignification to polymerize monolignols into oligo-lignols, cell-wall peroxidases may function when H202 is produced during the later stages of xylem cell development or in response to environmental stresses.

Natural Hypolignification Is Associated with Extensive Oligolignol Accumulation in Flax Stems

“…In support of this hypothesis, it is interesting that the five most abundant laccase transcripts in flax inner stem tissues are orthologs of the IRX12/AtLAC4 and AtLAC17 genes that have previously been shown to be involved in lignin formation in Arabidopsis (Brown et al, 2005;Berthet et al, 2011). The observation that three laccase gene transcripts are significantly more abundant in the upper region of inner stem tissues, whereas five peroxidase gene transcripts are more abundant in the lower region, could suggest that laccases are involved in the early stages of lignin formation followed by peroxidases, as hypothesized previously (Sterjiades et al, 1993). This idea is also supported by our results showing that three laccase transcripts and a transcript corresponding to the lignin gene COMT are significantly more abundant in the lower region of stem outer tissues, where lignification of bast fibers is first observed.…”

An Intracellular Laccase is Responsible for the Epicatechin Mediated Anthocyanin Degradation in Litchi Fruit Pericarp

“…They are ubiquitous enzymes that are found in plants, fungi, bacteria, and insects (Giardina et al, 2010). In plants, laccases participate in lignin biosynthesis, carrying out the oxidative polymerization of monolignols (Sterjiades et al, 1992(Sterjiades et al, , 1993Ranocha et al, 1999;Schuetz et al, 2014). These enzymes were also found to be involved in additional physiological processes, such as cytokinin homeostasis (Galuszka et al, 2005), resistance to phenolic pollutants (Wang et al, 2004), flavonoid polymerization in seed coats (Pourcel et al, 2005), and iron metabolism (Hoopes and Dean, 2004).…”

A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism

“…In the flax lignified bast fiber1 mutants, which have ectopic lignin formation in bast fibers, PEROXIDASE expression is increased in comparison with the wild type, suggesting that wild-type flax stems have insufficient peroxidase action, leading to the hypolignification of bast fibers. According to the current opinion in the field, laccases function in the initial coupling of monolignols to oligolignols, while peroxidases contribute to lignin formation at later stages (Sterjiades et al, 1993;Zhao et al, 2013). Additionally, some isoenzymes of them probably participate in the polymerization of proanthocyanidins (condensed tannins) detected in cells ( Fig.…”