Substrate Recognition and Specificity of Chitin Deacetylases and Related Family 4 Carbohydrate Esterases

Abstract

Carbohydrate esterases family 4 (CE4 enzymes) includes chitin and peptidoglycan deacetylases, acetylxylan esterases, and poly-N-acetylglucosamine deacetylases that act on structural polysaccharides, altering their physicochemical properties, and participating in diverse biological functions. Chitin and peptidoglycan deacetylases are not only involved in cell wall morphogenesis and remodeling in fungi and bacteria, but they are also used by pathogenic microorganisms to evade host defense mechanisms. Likewise, biofilm formation in bacteria requires partial deacetylation of extracellular polysaccharides mediated by poly-N-acetylglucosamine deacetylases. Such biological functions make these enzymes attractive targets for drug design against pathogenic fungi and bacteria. On the other side, acetylxylan esterases deacetylate plant cell wall complex xylans to make them accessible to hydrolases, making them attractive biocatalysts for biomass utilization. CE4 family members are metal-dependent hydrolases. They are highly specific for their particular substrates, and show diverse modes of action, exhibiting either processive, multiple attack, or patterned deacetylation mechanisms. However, the determinants of substrate specificity remain poorly understood. Here, we review the current knowledge on the structure, activity, and specificity of CE4 enzymes, focusing on chitin deacetylases and related enzymes active on N-acetylglucosamine-containing oligo and polysaccharides.

Mycoextraction: Rapid Cadmium Removal by Macrofungi-Based Technology from Alkaline Soil

“…Cell wall remolding was significantly induced under high Cd stress in the oyster mushroom fruiting body. A wide variety of cellular processes related to chitin modification, like carbohydrate esterase family 4, glycoside hydrolase family 18, glycosyltransferase family 4 [57][58][59], were upregulated in this study. Macrofungal cell wall, mainly composed of chitin [60], is known to participate in heavy metal detoxification [61].…”

Pectin Methylesterases: Cell Wall Remodeling Proteins Are Required for Plant Response to Heat Stress

“…Pectin methylesterases function in de-esterification of the methylated carboxyl group (COOCH 3 ) of pectin to form elastic pectins and accompany MeOH generation during division and maturation of the plant cell ( Komarova et al, 2014 ). Three modes of action of mature PMEs on polysaccharides have been proposed: single-chain, multiple-chain, and multiple-attack mechanisms ( Aragunde et al, 2018 ). In the single-chain mechanism, the activity of PME converts all substrate sites on the polymeric chain.…”

“…In the single-chain mechanism, the activity of PME converts all substrate sites on the polymeric chain. In the multiple-chain mechanism, PME catalyzes one reaction and then dissociates from the substrate, whereas PME catalyzes many cycles of reaction before the enzyme-polysaccharide complex dissociates in the multiple-attack mechanism ( Beigi et al, 2015 ; Aragunde et al, 2018 ). Both single-chain and multiple-attack mechanisms have been proposed in plant and bacterial PMEs as these produce contiguous regions of GalAs ( Christensen et al, 1998 ).…”

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