galakturonanu

Galakturonanu, often rendered as galacturonan in scientific contexts, is a polysaccharide composed of repeating units of D-galacturonic acid. The most common form is homogalacturonan, a linear polymer linked by α-(1→4) glycosidic bonds. Galacturonic acid residues can be partially methyl-esterified at the carboxyl group, yielding methyl galacturonate units; the degree of esterification affects gelling behavior and solubility.

Occurrence and biosynthesis: Galacturonan is a major component of plant cell walls and a principal constituent of pectin. It is synthesized in the Golgi apparatus of plant cells and secreted into the cell wall, where it can be further modified by enzymes such as pectin methylesterases, which remove methyl groups, altering interaction with calcium ions and other wall polymers.

Properties: As a hydrophilic polymer, galacturonan readily hydrates and forms gels under specific conditions. High-esterified forms tend to gel in the presence of sugar and acid, while low-esterified forms form calcium-mediated gels via the egg-box model. Its molecular weight and degree of esterification influence rheological properties and gel strength.

Applications: In food industry, galacturonan is a key thickener and gelling agent in products like jams and jellies. It also features in pharmaceuticals and cosmetics as a biocompatible excipient and can serve as a biomaterial scaffold in research settings.

Terminology: The term galakturonanu appears in some languages as a variant of galacturonan. In English, the standard terms are galacturonan or polygalacturonate.