Elongating β-1, 4-galactosyltransferase activity in mung bean (Vigna radiata) hypocotyls using 2-aminobenzaminated 1, 4-linked β-D-galactooligosaccharides as acceptor substrates

Abstract

Arabinan and galactan are side chaines of pectic polysaccharide, rhamnogalacturonan I (RG-I). They may involve in cell adhesion. But little is known about biosynthesis of galactan and arabinan. Bioassay of galactan is performed by determing incorporated ¹⁴ C-Gal from ¹⁴ C-labeled UDP-Gal. We prepared 2-aminobenzamide (2AB) -labeled galactooligosaccharides as acceptor substrates and determind galactosyltransferase (GalT) activity by HPLC, LC-ESI-MS, ¹ H NMR spectroscopy and enzyme hydrolysis. GalT transferred up to 14 Gals to the non reducing end of 2AB-labeled galactooligosacharides. The newly incorporated Gal residues were β-1,4 linked. 2AB-labeled RG-I having Gal residues was an acceptor substrate, suggesting that the GalT was capable to adding Gal residues to RG-I galactan side chains.