Pectin biosynthesis: a solubilized α1,4-galacturonosyltransferase from tobacco catalyzes the transfer of galacturonic acid from UDP-galacturonic acid onto the non-reducing end of homogalacturonan

Functional identification of an Arabidopsis pectin biosynthetic homogalacturonan galacturonosyltransferase

“…Both sequences are predicted to encode glycosyltransferases with type II membrane topology (23), C-terminal catalytic domains with consensus sequences clustered in CAZy glycosyltransferase family 8 (24), and to have basic isoelectric points. These characteristics are consistent with the known in vitro biochemical properties of GalATs (17,20). The predicted catalytic domains also contain DxD motifs, a conserved motif present in many well characterized glycosyltransferase families (25) and involved in the coordination of divalent cations (26).…”

“…Establishment of conditions to recover detergentsolubilized GalAT activity from membrane fractions (17) and in vitro studies using radiolabeled substrate (17) or fluorescently tagged (18,19) acceptors established that, in vitro, GalAT preferentially transfers GalA onto the nonreducing end (20) of HG oligosaccharide acceptors [oligogalacturonides (OGAs)] of a degree of polymerization (DP) Ͼ9 (17,18), although OGA acceptors as small as a trimer can be used (18,19). Polymeric pectins, such as poly-GalA and pectin, are less favorable substrates (21).…”

In VitroStabilization and Minimum Active Component of Polygalacturonic Acid Synthase Involved in Pectin Biosynthesis

“…Fax: +81-6-6850-5382; E-mail: txi@chem.sci.osaka-u.ac.jp Abbreviations: BES, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid; Bis-Tris, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid; DP, degree of polymerization; GalUA, galacturonic acid; HG, homogalacturonan; MES, 2-morpholinoethanesulfonic acid; MOPS, 3-morpholinopropanesulfonic acid; OGA, oligogalacturonic acid; PGA, polygalacturonic acid; PIPES, piperazine-1,4 0 -bis (2-ethanesulfonic acid) has been shown to add GalUA from UDP-GalUA onto the nonreducing end of oligogalacturonic acid (OGA). 18,20,21) It was found to be located in the lumen of the Golgi using sucrose density gradient centrifugation coupled with proteinase treatment of the Golgi-rich membrane fraction. 22) Recently, a new assay method for polygalacturonate 4--galacturonosyltransferase was developed using fluorescence-labeled OGAs as acceptor substrates.…”

Immunocytochemistry of the mucilage cells of Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae)

“…Approximately 80% of the residues of rhamnoses, in RG-I undergo substitutions by side chains, rich in arabinans and galactans (Krishnamurthy 1999, Scheller et al 1999, Pérez et al 2000. It is generally accepted that pectins are synthesized in a highly methylesterified form (Micheli 2001).…”