Glycosyl Glycerides

Monogalactosyldiglyceride (MGDG) and digalactosyldiglyceride (DGDG) are two important biomolecules that are especially prevalent in chloroplast membranes and photosynthetic tissues, including those of algae and some bacteria. MGDG is synthesized by MGDG synthase localized in chloroplast envelope membranes.1 DGDG is formed by the de-phosphorylation of phosphatidic acid or phosphatidylcholine and the subsequent reaction with two 5-diphosphate(UDP)-galactoses. A proper ratio of MGDG and DGDG is critical for membrane function. MGDG plays an important role in the organization and activity of the embedded protein supercomplexes of the thylalkoid membrane of photosystem II and it helps to maintain an optimum lipid to protein ratio.2 DGDG forms a lipid bilayer in the lipid membrane whereas MGDG does not.

References:

  1. Yoshiki Yamaryo et al. "In vitro reconstitution of monogalactosyldiacylglycerol (MGDG) synthase regulation by thioredoxin" FEBS Letters, Vol. 580:17 pp. 4086-4090, 2006
  2. Feng Zhou et al. "Effect of monogalactosyldiacylglycerol on the interaction between photosystem II core complex and its antenna complexes in liposomes of thylakoid lipids" Photosynthesis Research, Volume 99:3 pp. 185-193, 2009