Digalacturonic acid (DGA), derivedin vivofrom pectin catabolism, is used for the co-crystallization of enzymes such as proteinase K. It is used in galacturonic acid metabolism research as a substrate to identify, differentiate and characterized endo- and exopolygalacturonase(s) and gluconase(s). DGA is used to study the transport of oligogalacturonides by systems such as the TogMNAB ABC transporter.