Characterization of two 1,3-β-glucan-modifying enzymes from Penicillium sumatraense reveals new insights into 1,3-β-glucan metabolism of fungal saprotrophs

Abstract

Background 1,3-β-glucan is a polysaccharide widely distributed in the cell wall of several phylogenetically distant organisms, such as bacteria, fungi, plants and microalgae. The presence of highly active 1,3-β-glucanases in fungi evokes the biological question on how these organisms can efficiently metabolize exogenous sources of 1,3-β-glucan without incurring in autolysis. Results To elucidate the molecular mechanisms at the basis of 1,3-β-glucan metabolism in fungal saprotrophs, the putative exo-1,3-β-glucanase G9376 and a truncated form of the putative glucan endo-1,3-β-glucosidase (ΔG7048) from Penicillium sumatraense AQ67100 were heterologously expressed in Pichia pastoris and characterized both in terms of activity and structure. G9376 efficiently converted laminarin and 1,3-β-glucan oligomers into glucose by acting as an exo-glycosidase, whereas G7048 displayed a 1,3-β-transglucanase/branching activity toward 1,3-β-glucan oligomers with a degree of polymerization higher than 5, making these oligomers more recalcitrant to the hydrolysis acted by exo-1,3-β-glucanase G9376. The X-ray crystallographic structure of the catalytic domain of G7048, solved at 1.9 Å of resolution, consists of a (β/α)8 TIM-barrel fold characteristic of all the GH17 family members. The catalytic site is in a V-shaped cleft containing the two conserved catalytic glutamic residues. Molecular features compatible with the activity of G7048 as 1,3-β-transglucanase are discussed. Conclusions The antagonizing activity between ΔG7048 and G9376 indicates how opportunistic fungi belonging to Penicillium genus can feed on substrates similar for composition and structure to their own cell wall without incurring in a self-deleterious autohydrolysis.

Characterization of a Glycoside Hydrolase Family 157 Endo-β-1,3-Glucanase That Displays Antifungal Activity against Phytopathogens

“…β-1,3-Glucanases are PR-2 pathogenesis-related proteins, , which are strongly induced when plants respond to infection by bacterial, fungal, or viral pathogens. Previous studies indicated that β-1,3-glucanase can affect distortion during fruit growth and induce plant resistance to pathogenic fungi. − Since β-1,3-glucan is a constituent polysaccharide of the fungal cell wall, β-1,3-glucanase can destroy the fungal cell wall and, thus, inhibit fungal infection. Furthermore, the oligosaccharide hydrolysates of β-1,3-glucanase act as an elicitor to activate the immune signaling response of the plant. , In this work, after treatment with BsGlc157A solution, the mycelial growth of three pathogenic fungi (C.…”

“…Previous studies indicated that β-1,3-glucanase can affect distortion during fruit growth and induce plant resistance to pathogenic fungi. 33−35 Since β-1,3-glucan is a constituent polysaccharide of the fungal cell wall, 36 β-1,3-glucanase can destroy the fungal cell wall and, thus, inhibit fungal infection. Furthermore, the oligosaccharide hydrolysates of β-1,3-glucanase act as an elicitor to activate the immune signaling response of the plant.…”

BERBERINE BRIDGE ENZYME-LIKE OXIDASES OF CELLODEXTRINS AND MIXED-LINKED Β-Glucans CONTROL SEED COAT FORMATION

“…MALDI-MS analysis was performed according to Scafati et al (2022) with modifications. MS spectra of the sodium adducts of oligosaccharides [M + Na] + were performed with an UltraFlex MALDI-TOF/TOF mass spectrometer (Bruker, Germany).…”

A First Expression, Purification and Characterization of Endo-β-1,3-Glucanase from Penicillium expansum

“…All of these glucanases have a specific modifying function, some removing glucose from the end, and others increasing the β-glucan branching system of the fungus, making the fungus more resistant to its own hydrolysis activity. This characteristic enables the fungus to feed on glycannic nutrients without damaging the organism, thus justifying the specific interest for P. expansum glucanases [28].…”