BIOSYNTHESIS OF 1,2,3,6-TETRA-O-GALLOYL-β-D-GLUCOSE

Article abstract of DOI:10.1016/S0031-9422(00)95148-3

An enzyme that catalysed the β-glucogallin (1-O-galloyl-β-D-glucose)-dependent galloylation of 1,2,6-tri-O-galloyl-β-D-glucose to 1,2,3,6-tetra-O-galloyl-β-D-glucose was partially purified from leaves of the oak (Quercus robur).This acyltransferase had a M_r of ca 380000, and pH and temperature optima of 6.0 and 55 deg, respectively, and was most stable between pH 4.0 and 6.5.In addition to the natural substrates β-glucogallin (donor) and 1,2,6-trigalloylglucose (acceptor), 1,3,6-trigalloylglucose (which is not an intermediate in the biosynthesis of hydrolysable tannins in oak and sumac) was an equally efficient acceptor molecule; in both cases, 1,2,3,6-tetragalloylglucose was the reaction product.Based on the physiological role of this new enzyme, the systematic name "β-glucogallin: 1,2,6-tri-O-galloyl-β-D-glucose 3-O-galloyltransferase" (EC.2.3.1.-) is proposed. Key Word Index - Quercus robur (Q. pedunculata); Fagaceae; pedunculate oak; Rhus typhina; Anacardiaceae; staghorn sumac; biosynthesis; hydrolysable tannins; galloyltransferase; β-glucogallin; 1,2,6-tri-O-galloyl-β-D-glucose; 1,2,3,6-tetra-O-galloyl-β-D-glucose.