Oligogalacturonides

Oligogalacturonides (OGs) are short linear chains of α-1,4-linked D-galacturonic acid derived from pectin, the homogalacturonan component of plant cell walls. They are produced by hydrolysis of polygalacturonic acid via plant or microbial polygalacturonases or pectin lyases; depending on the enzymatic mode, non-reducing ends may carry an unsaturated residue. OGs commonly have degree of polymerization (DP) between 2 and about 25 and can vary in methyl esterification and acetylation, which influences solubility and biological activity.

In plants, OGs act as damage-associated molecular patterns (DAMPs) that alert and prime defenses. They are perceived by cell-surface receptors such as wall-associated kinases (WAKs) and other receptor-like kinases, triggering signaling cascades that lead to reactive oxygen species production, MAP kinase activation, hormone signaling, and expression of pathogenesis-related genes, often enhancing resistance to pathogens. The elicitor activity depends on DP and degree of esterification; certain unsaturated OGs from lyase action can be more active.

In mammals and humans, OGs have been reported to modulate immune responses in some contexts, including macrophage activation and cytokine production, with effects that appear to depend on DP, acetylation, and concentration. They can arise during digestion or food processing from pectin-containing foods. OGs are also studied as potential plant defense elicitors in agriculture and as research tools to probe pectin signaling.

Analytical and practical notes: OGs are commonly separated and characterized by size-exclusion chromatography or high-performance anion-exchange chromatography with pulsed amperometric detection, and mass spectrometry can determine DP and esterification pattern. They are typically produced commercially by controlled pectin degradation for research use.