Oxalate decarboxylase of the white-rot fungus Dichomitus squalens demonstrates a novel enzyme primary structure and non-induced expression on wood and in liquid cultures

Abstract

Oxalate decarboxylase (ODC) catalyses the conversion of oxalic acid to formic acid and CO 2 in bacteria and fungi. In wood-decaying fungi the enzyme has been linked to the regulation of intraand extracellular quantities of oxalic acid, which is one of the key components in biological decomposition of wood. ODC enzymes are biotechnologically interesting for their potential in diagnostics, agriculture and environmental applications, e.g. removal of oxalic acid from industrial wastewaters. We identified a novel ODC in mycelial extracts of two wild-type isolates of Dichomitus squalens, and cloned the corresponding Ds-odc gene. The primary structure of the Ds-ODC protein contains two conserved Mn-binding cupin motifs, but at the N-terminus, a unique, approximately 60 aa alanine-serine-rich region is found. Real-time quantitative RT-PCR analysis confirmed gene expression when the fungus was cultivated on wood and in liquid medium. However, addition of oxalic acid in liquid cultures caused no increase in transcript amounts, thereby indicating a constitutive rather than inducible expression of Ds-odc. The detected stimulation of ODC activity by oxalic acid is more likely due to enzyme activation than to transcriptional upregulation of the Ds-odc gene. Our results support involvement of ODC in primary rather than secondary metabolism in fungi.

CO2Migration Pathways in Oxalate Decarboxylase and Clues about Its Active Site

“…5 −10 OXDC has been well characterized in several fungi such as Aspergillus niger, 11 Postia placenta, 12 Flammulina velutipes, 13 and Dichomitus squalens. 14 The structure of the first bacterial OXDC, from Bacillus subtilis, was determined and studied by Anand et al in 2002. 15 OXDC is a protein of the cupin superfamily and exists in the bicupin structure (see Figure 1).…”

Observation of superoxide production during catalysis of Bacillus subtilis oxalate decarboxylase at pH 4

“…OxDC is utilized by soil bacteria and fungi and plays an important role in the biogeochemical carbon cycle facilitating the oxalate-carbonate pathway [11]. It accumulates in the cell wall of Bacillus subtilis and can be secreted by many basidiomycetous and ascomycetous fungi [11, 12]. OxDC has garned attention due to its potentially numerous applications ranging from remediation of oxalate scaling in the wood and paper industry [13–16], bioengineering of crop plants for fungal resistance and lower oxalate content [17, 18], diagnostics and sensing of oxalate [19–21], bioengineering of probiotic gut bacteria to release OxDC in the intestine [22], and as a dietary supplement for the degradation of excess oxalate in the stomach [23, 24].…”

Primer Sets Developed for Functional Genes Reveal Shifts in Functionality of Fungal Community in Soils

“…This is in accordance with the assumption that this gene may be involved in degradation of fungal hyphae and not involved in the decomposition of plant derived material (Hartl et al, 2012). Surprisingly, oxalate decarboxylase composition was not related to lignin degradation pathways even though it is known to be involved in regulation of intra- and extracellular quantities of oxalic acid, which is one of the key components in biological decomposition lignin (Mäkelä et al, 2009). In this system the composition of oxalate decarboxylases seems to, however, be linked to GHs from families 10 and 74 and to nitrogen uptake by Ascomycota.…”