AA9 and AA10: from enigmatic to essential enzymes

Abstract

The lignocellulosic biomass, comprised mainly of cellulose, hemicellulose, and lignin, is a strong competitor for petroleum to obtain fuels and other products because of its renewable nature, low cost, and non-competitiveness with food production when obtained from agricultural waste. Due to its recalcitrance, lignocellulosic material requires an arsenal of enzymes for its deconstruction and the consequent release of fermentable sugars. In this context, enzymes currently classified as auxiliary activity 9 (AA9/formerly GH61) and 10 (AA10/formerly CBM 33) or lytic polysaccharide monooxygenases (LPMO) have emerged as cellulase boosting enzymes. AA9 and AA10 are the new paradigm for deconstruction of lignocellulosic biomass by enhancing the activity and decreasing the loading of classical enzymes to the reaction and, consequently, reducing costs of the hydrolysis step in the second-generation ethanol production chain. In view of that disclosed above, the goal of this work is to review experimental data that supports the relevance of AA9 and AA10 for the biomass deconstruction field.

Activating Intrinsic Carbohydrate-Active Enzymes of the Smut Fungus Ustilago maydis for the Degradation of Plant Cell Wall Components

“…More complex substrates, however, will need the simultaneous action of different enzymes (70). Efficient degradation of cellulose, for example, requires the simultaneous action of endoglucanase, ␤-glucosidase, cellobiohydrolase I and II, and lytic polysaccharide monooxygenase, as well as several accessory factors (10,71). Also, complete hemicellulose hydrolysis is based on the action of multiple enzymes (72).…”

Biochemical and biophysical properties of a metagenome-derived GH5 endoglucanase displaying an unconventional domain architecture

“…The classical scheme for hydrolytic cellulose degradation involves at least three types of enzyme activities working synergistically: (i) endo-1,4-␤-glucanases, which randomly cleave internal bonds of the cellulose chain, (ii) exo-1,4-␤-glucanases, which hydrolyze the external bonds of the reducing or non-reducing end of the chain and (iii) ␤-glucosidases, that cleave cellobiose molecules to glucose [9]. Recently, lytic polysaccharide monooxygenases (LPMOs) have been recognized as important players in the improvement of cellulose degradation by acting in synergy with cellulases [9,10].…”

Reactivity of O 2 versus H 2 O 2 with polysaccharide monooxygenases

“…Cu-dependent polysaccharide monooxygenases (PMOs), also known as lytic PMOs, are found in eukaryotic and prokaryotic organisms (2) and are secreted into the extracellular environment to degrade polysaccharides through an oxidative mechanism. Over the past decade, research on this enzyme family has intensified as PMOs have emerged as potential catalysts in biofuel production (3,4) and have been implicated in various physiological processes (5,6).…”