**1. Introduction**

Lignocellulolytic enzymes comprise cellulases, hemicellulases, and ligninases, which respectively degrade cellulose, hemicellulose, and lignin, the main constituents of plant cell wall, which collectively are named lignocellulose. Cellulases are employed in many industrial sectors, such as textile [1], detergents [2], animal feed, and vinification [2–5]. In the last years, the potential of these enzymes to saccharify cellulose from lignocellulosic residues has been extensively studied aiming the use of glucose for cellulosic ethanol production [6]. Hemicellulases are used in biobleaching of Kraft pulp for paper production [7, 8], bioclarification of fruit juices [9], and obtainment of C5 and C6 sugars from lignocellulosic residues, in the context of second-generation ethanol production [10]. Finally, ligninases are used in paper, textile, cosmetic, and pharmaceutical industries, in bioremediation and wastewater treatment [11, 12],

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

in organic synthesis, and in biological pretreatment of lignocellulosic residues [13] to be used for cellulosic ethanol production.

Many studies have elucidated how cellulases bind to their substrates, as well as their catalytic mechanisms [14–17]. The modes of action of hemicellulases and ligninases have also been explored [18, 19]. The knowledge about these enzymes activators and inhibitors is also relevant, mainly in the context of industrial applications. Metal ions, for example, influence

**Figure 1.** General distribution of activators and inhibitors of lignocellulases. HMF furfural: hydroxymethyl furfural; LPMOs: lytic polysaccharide monooxygenases; XEGIP: xyloglucan-endo-β-glucanase inhibitor proteins; XOS: xylooligosaccharides; SDS: sodium dodecyl sulfate; TAXI: *T*. xylanase inhibitor; XIP: xylanase inhibitor protein; TLXI: thaumatin-like xylanase inhibitor.

these enzymes activities and may be present in water and/or other reagents employed in industrial processes or may result from equipment corrosion [20]. However, the interference mechanisms are not well understood. There is also a lack of data to corroborate if the inhibition or activation occurs via allosteric or nonallosteric mechanism. So, this chapter presents a brief review of the main activators and inhibitors of lignocellulolytic enzymes, which are summarized in **Figure 1**.
