Family

Fungal ligninase (IPR001621)

Short name: Ligninase

Family relationships

None.

Description

Peroxidases are haem-containing enzymes that use hydrogen peroxide as the electron acceptor to catalyse a number of oxidative reactions. Peroxidases are found in bacteria, fungi, plants and animals. Fungal ligninases are extracellular haem enzymes involved in the degradation of lignin. They include lignin peroxidases (LiPs), manganese-dependent peroxidases (MnPs) and versatile peroxidases, which combine the substrate-specificity characteristics of the other two [PMID: 10187820]. In MnP, Mn2+ serves as the reducing substrate [PMID: 8167033].

It is commonly thought that the plant polymer lignin is the second most abundant organic compound on Earth, exceeded only by cellulose. Higher plants synthesise vast quantities of insoluble macromolecules, including lignins. Lignin is an amorphous three-dimensional aromatic biopolymer composed of oxyphenylpropane units. Biodegradation of lignins is slow - it is probable that their decomposition is the rate-limiting step in the biospheric carbon-oxygen cycle, which is mediated almost entirely by the catabolic activities of microorganisms. The white-rot fungi are able extensively to decompose all the important structural components of wood, including both cellulose and lignin. Under the proper environmental conditions, white-rot fungi completely degrade all structural components of lignin, with ultimate formation of CO2 and H2O. The first step in lignin degradation is depolymerisation, catalysed by the LiPs (ligninases). LiPs are secreted, along with hydrogen peroxide (H2O2), by white-rot fungi under conditions of nutrient limitation. The enzymes are not only important in lignin biodegradation, but are also potentially valuable in chemical waste disposal because of their ability to degrade environmental pollutants [PMID: 8167033].

To date, 3D structures have been determined for LiP [PMID: 8440725] and MnP [PMID: 7806497] from Phanerochaete chrysosporium (White-rot fungus), and for the fungal peroxidase from Arthromyces ramosus [PMID: 8289254]. All these proteins share the same architecture and consist of 2 all-alpha domains, between which is embedded the haem group. The helical topography of LiPs is nearly identical to that of yeast cytochrome c peroxidase (CCP) [PMID: 7922023], despite the former having four disulphide bonds, which are absent in CCP (MnP has an additional disulphide bond at the C terminus).

GO terms

Biological Process

GO:0055114 oxidation-reduction process
GO:0006979 response to oxidative stress

Molecular Function

GO:0020037 heme binding
GO:0004601 peroxidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
CDD
PRINTS