Catalytic Diversity of GH30 Xylanases

Abstract

Catalytic properties of GH30 xylanases belonging to subfamilies 7 and 8 were compared on glucuronoxylan, modified glucuronoxylans, arabinoxylan, rhodymenan, and xylotetraose. Most of the tested bacterial GH30-8 enzymes are specific glucuronoxylanases (EC 3.2.1.136) requiring for action the presence of free carboxyl group of MeGlcA side residues. These enzymes were not active on arabinoxylan, rhodymenan and xylotetraose, and conversion of MeGlcA to its methyl ester or its reduction to MeGlc led to a remarkable drop in their specific activity. However, some GH30-8 members are nonspecific xylanases effectively hydrolyzing all tested substrates. In terms of catalytic activities, the GH30-7 subfamily is much more diverse. In addition to specific glucuronoxylanases, the GH30-7 subfamily contains nonspecific endoxylanases and predominantly exo-acting enzymes. The activity of GH30-7 specific glucuronoxylanases also depend on the presence of the MeGlcA carboxyl, but not so strictly as in bacterial enzymes. The modification of the carboxyl group of glucuronoxylan had only weak effect on the action of predominantly exo-acting enzymes, as well as nonspecific xylanases. Rhodymenan and xylotetraose were the best substrates for exo-acting enzymes, while arabinoxylan represented hardly degradable substrate for almost all tested GH30-7 enzymes. The results expand current knowledge on the catalytic properties of this relatively novel group of xylanases.

Characterization of a novel GH30 non-specific endoxylanase AcXyn30B from Acetivibrio clariflavus

“…GH30 enzymes active on xylan have so far been found in the subfamilies GH30_7, GH30_8, and GH30_10 (Puchart et al 2021 ). While bacterial GH30_8 members are mostly specific glucuronoxylanases (EC 3.2.1.136) requiring MeGlcA substitution of the xylan chain for their activity (St. John et al 2006 ; Vršanská et al 2007 ), fungal GH30_7 members show broader substrate specificity (Šuchová et al 2021b ). In addition to specific glucuronoxylanases (Biely et al 2014 ), the GH30_7 subfamily contains non-specific endo-β-1,4-xylanases (EC 3.2.1.8) (Nakamichi et al 2019c ; Šuchová et al 2021c ), reducing end xylose releasing xylanases (Rex-es, EC 3.2.1.156) (Tenkanen et al 2013 ; Nakamichi et al 2019a ), xylobiohydrolases (acting at the non-reducing end) (Šuchová et al 2020 ) and bifunctional glucuronoxylanases/xylobiohydrolases (Nakamichi et al 2019b ; Katsimpouras et al 2019 ).…”

Structural and molecular insights into a bifunctional glycoside hydrolase 30 xylanase specific to glucuronoxylan

“…The present work focuses on a glycoside hydrolase 30 subfamily 7 (GH30_7) xylanase from the thermophilic fungus Themothelomyces thermophila , named Tt Xyn30A (Drula et al, 2022; Katsimpouras et al, 2019). GH30_7 xylanases are mainly of fungal origin and exhibit diverse modes of action, such as nonreducing end specific xylobiohydrolases, and appendage‐dependent endo‐ β ‐1,4‐xylanases, as well as bi‐functional enzymes, attracting interest, particularly in the field of protein engineering (Drula et al, 2022; Šuchová et al, 2021). The GH30 appendage‐dependent xylanases generate substituted XOs of specific structure, in contrast to GH10 and GH11 endo‐xylanases, which generally display lower selectivity for MeGlcA‐substituted xylan (Nordberg Karlsson et al, 2018).…”

Yeast GH30 Xylanase from Sugiyamaella lignohabitans Is a Glucuronoxylanase with Auxiliary Xylobiohydrolase Activity

“…Most EXs are classified in glycoside hydrolase (GH) families 10 and 11 ( , accessed on 1 December 2021) [ 1 ]; however, they are also found in GH families 5, 8, 30, 43, 98 and 141. During the last few years, great attention has been paid to the EXs from GH30 family [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Prokaryotic EXs are grouped into subfamily GH30-8, while eukaryotic xylanases are members of GH30-7 subfamily.…”

“…Catalytic properties of the GH30-8 subfamily enzymes are quite uniform and most of them are specific glucuronoxylanases (EC 3.2.1.136) requiring glucuronic or 4- O -methyl-glucuronic acid (MeGlcA) substitution of the main chain for their action [ 13 , 14 , 15 ]. On the other hand, catalytic properties of the GH30-7 subfamily representatives are diverse and include specific glucuronoxylanases, xylobiohydrolases, non-specific endoxylanases, endoxylanases/xylobiohydrolases and xylanases releasing xylose from the reducing end of the substrate [ 11 , 12 ]. All characterized GH30-7 xylanases come from filamentous fungi and so far no yeast GH30 EX has been described.…”