Rhamnogalacturonan Endolyase Family 4 Enzymes: An Update on Their Importance in the Fruit Ripening Process

Fruit ripening is a process that produces fruit with top sensory qualities that are ideal for consumption. For the plant, the final objective is seed dispersal. One of the fruit characteristics observed by consumers is texture, which is related to the ripening and softening of the fruit. Controlled and orchestrated events occur to regulate the expression of genes involved in disassembling and solubilizing the cell wall. Studies have shown that changes in pectins are closely related to the loss of firmness and fruit softening. For this reason, studying the mechanisms and enzymes that act on pectins could help to elucidate the molecular events that occur in the fruit. This paper provides a review of the enzyme rhamnogalacturonan endolyase (RGL; EC 4.2.2.23), which is responsible for cleavage of the pectin rhamnogalacturonan I (RGL-I) between rhamnose (Rha) and galacturonic acid (GalA) through the mechanism of β-elimination during fruit ripening. RGL promotes the loosening and weakening of the cell wall and exposes the backbone of the polysaccharide to the action of other enzymes. Investigations into RGL and its relationship with fruit ripening have reliably demonstrated that this enzyme has an important role in this process. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.