Fungal glycoside hydrolase family 44 xyloglucanases are restricted to the phylum Basidiomycota and show a distinct xyloglucan cleavage pattern

Peicheng Sun; Xinxin Li; Adiphol Dilokpimol; Bernard Henrissat; Ronald P de Vries; Mirjam A Kabel; Miia R Mäkelä

doi:10.1016/j.isci.2021.103666

Fungal glycoside hydrolase family 44 xyloglucanases are restricted to the phylum Basidiomycota and show a distinct xyloglucan cleavage pattern

iScience. 2021 Dec 21;25(1):103666. doi: 10.1016/j.isci.2021.103666. eCollection 2022 Jan 21.

Authors

Peicheng Sun¹, Xinxin Li², Adiphol Dilokpimol², Bernard Henrissat^{3

4}, Ronald P de Vries², Mirjam A Kabel¹, Miia R Mäkelä⁵

Affiliations

¹ Laboratory of Food Chemistry, Wageningen University and Research, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands.
² Fungal Physiology, Westerdijk Fungal Biodiversity Institute and Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
³ DTU Bioengineering, Technical University of Denmark, Søltofts Plads, 2800 Kongens Lyngby, Denmark.
⁴ Department of Biological Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
⁵ Department of Microbiology, University of Helsinki, Viikinkaari 9, 00790 Helsinki, Finland.

Abstract

Xyloglucan is a prominent matrix heteropolysaccharide binding to cellulose microfibrils in primary plant cell walls. Hence, the hydrolysis of xyloglucan facilitates the overall lignocellulosic biomass degradation. Xyloglucanases (XEGs) are key enzymes classified in several glycoside hydrolase (GH) families. So far, family GH44 has been shown to contain bacterial XEGs only. Detailed genome analysis revealed GH44 members in fungal species from the phylum Basidiomycota, but not in other fungi, which we hypothesized to also be XEGs. Two GH44 enzymes from Dichomitus squalens and Pleurotus ostreatus were heterologously produced and characterized. They exhibited XEG activity and displayed a hydrolytic cleavage pattern different from that observed in fungal XEGs from other GH families. Specifically, the fungal GH44 XEGs were not hindered by substitution of neighboring glucosyl units and generated various "XXXG-type," "GXXX(G)-type," and "XXX-type" oligosaccharides. Overall, these fungal GH44 XEGs represent a novel class of enzymes for plant biomass conversion and valorization.

Keywords: Biomass; Enzymology; Mycology.