β-Glucosidases in specialized metabolism: Towards a new understanding of the gatekeepers of plant chemical arsenal

Plants produce an exceptional multitude of chemicals to compensate with challenging environments. Despite the structural pluralism of specialized metabolism, often defensive compounds are stored in planta as glycosides and reactive aglycones are conditionally activated by specific β-glucosidases—a large family of enzymes with pluripotent contribution in homeostasis and a pivotal role in plant chemical defense. Typically, these detonating enzymes are characterized by exceptional substrate specificity and, in several cases, even isoenzymes exhibit differentiated molecular or biochemical characteristics. This article focuses on important intrinsic characteristics of plant β-glucosidases detonating defensive compounds and highlights recent studies with novel implications in regulatory mechanisms.