Understanding the structural and functional properties of carbohydrate esterases with a special focus on hemicellulose deacetylating acetyl xylan esterases

Abstract

Acetyl and methyl esterifications are two major naturally found substitutions in the plant cell-wall polysaccharides. The non-cellulosic plant cell-wall polysaccharides such as pectin and hemicellulose are differentially esterified by the O-acetyl and methyl groups to cease the action of various hydrolytic enzymes secreted by different fungi and bacterial species. Thus, microorganisms have emerged with a special class of enzymes known as carbohydrate esterases (CE). The CE catalyse O-de, N-deacetylation of acetylated saccharide residues (esters or amides, where sugars play the role of alcohol/amine/acid). Carbohydrate active enzyme (CAZy) database has classified CE into 16 classes, of which hemicellulose deacetylating CE were grouped into eight classes (CE-1 to CE-7 and CE-16). Various plant biomass degrading fungi and bacteria secretes acetyl xylan esterases (AcXE); however, these enzymes exhibit varied substrate specificities. AcXE and xylanases-coupled pretreatment methods exhibit significant applications, such as enhancing animal feedstock, baking industry, production of food additives, paper and pulp, xylitol production and biorefinery-based industries, respectively. Thus, understanding the structural and functional properties of acetyl xylan esterase will significantly aid in developing the efficient AcXE with wide range of industrial applications.

Insight into plant cell wall degradation and pathogenesis of Ganoderma boninense via comparative genome analysis

“…The genome of G. boninense NJ3 was well-represented with CE16 in addition to CE1 and CE12 that were also found in necrosis-causing M. perniciosa, A. solidipes and A. mellea while CE2, CE14 and high copies of CE10 were found only in the pathogenic Ganoderma spp. CEs have been associated in the first line of attack during fungal invasion via the removal of acetylated moieties of saccharides that formed parts of plant protection system against hydrolytic enzymes (Ospina-Giraldo, McWalters & Seyer, 2010; Sista Kameshwar & Qin, 2018). The CE10 enzyme is involved in the degradation of lignin and cellulosic components of the plant cell wall and was found to be abundant in several pathogenic fungi including Macrophomina phaseolina , Bipolaris cookei and Corynespora cassiicola (Islam et al, 2012; Zaccaron & Bluhm, 2017; Looi et al, 2017).…”

Characterization of glycoside hydrolase family 11 xylanase from Streptomyces sp. strain J103; its synergetic effect with acetyl xylan esterase and enhancement of enzymatic hydrolysis of lignocellulosic biomass

“…Due to the addition of AXE, the relative activity of cXyl was enhanced by 1.37-fold than that of rXynS1 alone. AXE increases the accessibility of xylanase enzymes to the substrates, as most of the acetyl groups present in the xylan chain can hinder xylanase activity [ 59 ]. Thus, it is important to perform deacetylation efficiently, to increase the hydrolysis yield of xylan and produce non-acetylated hydrolysis products [ 60 ].…”

Systematic review of publicly available non-Dikarya fungal proteomes for understanding their plant biomass-degrading and bioremediation potentials

“…Hemicellulose is a complex hetero-polysaccharide composed of glucomannan, xylan, glucuronoxylan, arabinoxylan and xyloglucan, In plant cell walls, hemicellulose is found in close associations with lignin, cellulose and pectin units (Scheller and Ulvskov 2010;Sista Kameshwar and Qin 2018). Thus, structurally complex hemicellulose depends on a wide range of enzymes for its degradation and conversion to simple monomers.…”