Biosynthesis of gallotannins: beta-glucogallin-dependent formation of 1,2,3,4,6-pentagalloylglucose by enzymatic galloylation of 1,2,3,6-tetragalloylglucose.
An acyltransferase was detected in young leaves of pedunculate oak (Quercus robur) that catalyzed the formation of 1,2,3,4,6-penta-O-galloyl-beta-D-glucose, the common precursor of gallotannins and the related ellagitannins. This enzyme depended on beta-glucogallin (1-O-galloyl-beta-D-glucose) as acyl donor; 1,2,3,6-tetra-O-galloyl-beta-D-glucose was specifically required as acceptor molecule, whereas no reaction occurred with the 1,2,4,6-isomer of this substrate. The partially purified enzyme (Mr 260,000) was stable between pH 5.0 and 6.5; highest activities were observed at pH 6.3 and 40 degrees C. Km values of 2.3 and 1.0 mM, respectively, were determined for the substrates beta-glucogallin and tetragalloylglucose. In accordance with stoichiometric studies, the systematic name "beta-glucogallin: 1,2,3,6-tetra-O-galloylglucose 4-O-galloyltransferase" is proposed for this new enzyme.
Cammann
J
J
Universität Ulm, Abteilung Allgemeine Botanik, Ulm, Federal Republic of Germany.
Denzel
K
K
Schilling
G
G
Gross
G G
GG
D000217:Acyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism; D005947:Glucose / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D047348:Hydrolyzable Tannins / Q000096:biosynthesis*; D009682:Magnetic Resonance Spectroscopy; D013634:Tannins / Q000096:biosynthesis*; D014197:Trees
D047348:Hydrolyzable Tannins; D013634:Tannins; C435084:pentagalloylglucose; C060474:glucogallin; D005707:Gallic Acid; C060475:1,2,3,6-tetragalloylglucose; D000217:Acyltransferases; D005947:Glucose