Gallotannin

A gallotannin is any of a class of molecules belonging to the hydrolysable tannins. Gallotannins are polymers formed when gallic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.

Metabolism

Gallate 1-beta-glucosyltransferase uses UDP-glucose and gallate to produce UDP and 1-galloyl-beta-D-glucose. Beta-glucogallin O-galloyltransferase uses 1-O-galloyl-beta-D-glucose to produce D-glucose and 1-O,6-O-digalloyl-beta-D-glucose. Beta-glucogallin-tetrakisgalloylglucose O-galloyltransferase uses 1-O-galloyl-beta-D-glucose and 1,2,3,6-tetrakis-O-galloyl-beta-D-glucose to produce D-glucose and 1,2,3,4,6-pentakis-O-galloyl-beta-D-glucose (1,2,3,4,6-penta-O-galloyl-β-D-glucose, the common precursor of gallotannins and the related ellagitannins).^[1]

Tannase is a key enzyme in the degradation of gallotannins that uses digallic acid and H₂O to produce gallic acid.

References

^ Cammann, Jessica; Denzel, Klaus; Schilling, Gerhard; Gross, Georg G. (August 1989). "Biosynthesis of gallotannins: β-Glucogallin-dependent formation of 1,2,3,4,6-pentagalloylglucose by enzymatic galloylation of 1,2,3,6-tetragalloylglucose". Archives of Biochemistry and Biophysics. 273 (1): 58–63. doi:10.1016/0003-9861(89)90161-6. PMID 2757399.

Types of gallotannins

Aglycones

Galloyl glucoses

1-Galloyl glucose Glucogallin
Digalloyl glucoses:	1,6-Digalloyl glucose 2,6-Digalloyl glucose 3,6-digalloyl glucose
Trigalloyl glucoses:	1,2,3-Trigalloyl glucose 1,2,3-tri-O-galloyl-β-D-glucose 1,2,6-Trigalloyl glucose / 1,3,6-Trigalloyl glucose
Tetragalloyl glucoses:	1,2,3,6-tetragalloylglucose 1,2,3,6-tetra-O-galloyl-β-D-glucose 1,2,4,6-Tetragalloyl glucose 1,2,4,6-tetra-O-galloyl-β-D-glucose
Pentagalloyl glucose:	1,2,3,4,6-Pentagalloyl-glucose 6-digalloyl-1,2,3-trigalloyl-glucose
other	Hexagalloyl glucose Heptagalloyl glucose Octagalloyl glucose Nonagalloyl glucose Decagalloyl glucose

Galloyl quinic acids

Galloyl quinic acids:	3-O-Galloylquinic acid theogallin 4-O-Galloylquinic acid 5-O-Galloylquinic acid
Digalloyl quinic acids:	1,4-Di-O-galloylquinic acid 3,4-di-O-Galloylquinic acid 3,5-di-O-Galloylquinic acid 4,5-di-O-Galloylquinic acid
Trigalloyl quinic acids:	1,3,4-Tri-O-galloylquinic acid 3,4,5-Tri-O-galloylquinic acid