Characterization of a GH36 α-D-Galactosidase Associated with Assimilation of Gum Arabic in Bifidobacterium longum subsp. longum JCM7052

Abstract

We recently characterized a 3-O-α-D-galactosyl-α-L-arabinofuranosidase (GAfase) for therelease of α-D-Gal-(1→3)-L-Ara from gum arabic arabinogalactan protein (AGP) in Bifidobacteriumlongum subsp. longum JCM7052. In the present study, we cloned and characterized a neighboring α-galactosidase gene (BLGA_00330; blAga3). It contained an Open Reading Frame of 2151-bp nucleotidesencoding 716 amino acids with an estimated molecular mass of 79,587 Da. Recombinant BlAga3released galactose from α-D-Gal-(1→3)-L-Ara, but not from intact gum arabic AGP, and a littlefrom the related oligosaccharides. The enzyme also showed the activity toward blood group B linertrisaccharide. The specific activity for α-D-Gal-(1→3)-L-Ara was 4.27- and 2.10-fold higher thanthose for melibiose and raffinose, respectively. The optimal pH and temperature were 6.0 and 50 °C,respectively. BlAga3 is an intracellular α-galactosidase that cleaves α-D-Gal-(1→3)-L-Ara produced byGAfase; it is also responsible for a series of gum arabic AGP degradation in B. longum JCM7052.