A gallotannin is any of a class of molecules belonging to the

hydrolysable tannin A hydrolyzable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids. At the center of a hydrolyzable tannin molecule, there is a carbohydrate (usually D-glucose ...

s. Gallotannins are polymers formed when

gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. I ...

, a polyphenol monomer, esterifies and binds with the hydroxyl group of a

polyol In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thr ...

carbohydrate such as glucose.

Metabolism

Gallate 1-beta-glucosyltransferase In enzymology, a gallate 1-beta-glucosyltransferase () is an enzyme that catalyzes the chemical reaction :UDP-glucose + gallate \rightleftharpoons UDP + 1-galloyl-beta-D-glucose Thus, the two substrates of this enzyme are UDP-glucose and gall ...

uses

UDP-glucose Uridine diphosphate glucose (uracil-diphosphate glucose, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism. Functions UDP-glucose is used in nucleotide sugar metabolism as an activated form of gl ...

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 Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usin ...

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 Onekama ( ) is a village in Manistee County in the U.S. state of Michigan. The population was 411 at the 2010 census. The village is located on the shores of Portage Lake and is surrounded by Onekama Township. The town's name is derived from "O ...

to produce

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 ellagitanninsBiosynthesis of gallotannins: β-Glucogallin-dependent formation of 1,2,3,4,6-pentagalloylglucose by enzymatic galloylation of 1,2,3,6-tetragalloylglucose. Cammann J., Denzel K., Schilling G. and Gross G. G., Archives of Biochemistry and Biophysics, Volume 273, Issue 1, 15 August 1989, Pages 58-63
/ref>). Tannase is a key enzyme in the degradation of gallotannins that uses

digallic acid Digallic acid is a polyphenolic compound found in ''Pistacia lentiscus''. Digallic acid is also present in the molecule of tannic acid. Digalloyl esters involve either ''-meta'' or ''-para'' depside bonds. Tannase is an enzyme that uses digalla ...

and H₂O to produce

References

{{Gallotannin Gallotannins

Metabolism

See also

References