## 4 Discussion
### In Silico Analysis of Carbohydrate Metabolism of C. leave
The latter, in turn, is a product of glucose oxidation by glucose oxidase (GOX, EC 1.1.3.4) or oxidative degradation of glucose-containing polysaccharides (e.g., cellulose, xyloglucan, etc.) with LPMOs and/or FAD-oligosaccharide oxidase (AA7 CAZymes) identified in the fungal secretomes. Under neutral or alkaline conditions, D-glucono-1,5-lactone undergoes spontaneous hydrolysis. As the reaction proceeds and D-gluconic acid (D-gluconate) accumulates, the medium becomes acidic. The lactones are then enzymatically hydrolyzed in the presence of lactonase (EC 3.1.1.17). After intracellular penetration, D-gluconate is metabolized via the PPP (KEEG pathway: map00030). It is noteworthy that the TFK32984.1 protein representing gluconolactone (EC 3.1.1.17), which hydrolyzes D-glucono-1,5-lactone to gluconic acid, was detected in the GP medium where D-glucose was the only carbohydrate. In addition to gluconolactone, seven other genes encoding the proteins TFK32977.1, TFK33000.1, TFK35654.1, TFK32978.1, TFK31125.1, TFK37132.1 and TFK32978.1 were predicted in the _C. laeye_ genome. According to the COG database, this protein belongs to the YvrE superfamily (COG3386) which includes sugar lactone lactonases. In contrast, no lactonase genes were found in the WRF _P. chrysosporium_ genome, and two copies were detected in the genome of _Dichomitus squalens_[77]. The presence of eight sugar lactone lactones genes in the _C. laeee_ genome, with quite low levels of amino acid sequence identity (from less than 50 to 86% identity), may indicate the preferential catabolism of various oxidized sugars resulting from the enzymatic oxidation of lignocellulosic. This correlated with the detection of several genes of LPMOs, AA3_2 and AA7 CAZymes. Such special catabolic behavior, the ability to metabolize aldomic acids (such as D-gluconate), appears to confer certain environmental advantages on forest floor fungi, since the rapid oxidation of glucose and other monosaccharides released during the destruction of plant cell wall polysaccharides prevents carbohydrate use by competitive microorganisms, which are abundant in the econiche of the forest floor. Perhaps, such a longer glycolysis metabolic pathway, compared to D-glucose catabolism, results in a rather low growth rate of _C. laeee_. The _C. laeee_ genome contains all enzymes of the Leloir pathway (KEGG pathway: map00052) and some enzymes of the unphosphorylated De Lay-Doudoroff pathway of D-galactose metabolism (Figure 8B, Supplementary Table S5). Overall, at least one gene for mannose and L-rhamnose metabolism was identified in the _C. laeee_ genome (Supplementary Table S5). Key genes for L-arabinose metabolism are absent from the _C. laeee_ genome, in contrast to D-xylose metabolism, where some of them are present in multiple copies, in particular the genes for xylitol dehydrogenase (EC 1.1.1.9) and D-xylulose kinase (EC 2.7.1.17) (Figure 8B, Supplementary Table S5). It is possible that _C. laeee_ is unable to metabolize L-arabinose and this may explain the lower growth rate on arabin xylan again medium than on other hemicellulose polysaccharides (Figure 2). All genes involved in D-ribose catabolism are also present in the _C. laeee_ genome (Figure 8B, Supplementary Table S5). Further detailed studies of carbohydrate metabolism in _C. laeee_ are required.