Studies on Galactanases and Their Transfer Reaction

Abstract

1. Galactanasses from Penicillium citrinum and Bacillus subtilis were purified and char-acterized. Two galactanases from P. citrinum had essentially the same properties and hydrolyzed β-1, 4-galactosidic linkages of soybean arabinogalactan (SAG) in an endo-manner. B. subtilis galactanase was an exo-enzyme which hydrolyzed SAG and oligosaccharides to produce galac-toboise from the non-reducing ends. 2. Transfer reaction catalyzed by the galactanases were studied. The P. citrinum enzyme degraded o-nitrophenyl-β-galactoside after a lag phase. A reaction mechanism which involved transglycosylation in addition to hydrolysis was proposed. The endo- and exo-galactanases showed broad acceptor specificities and transglycosylated various alcohols, phenols, sugar alcohols, and saccharides. Structural feature of the products from glycerol was different among the galactanases and Escherichia coli β-galactosidase : the galactanases transglycosylated preferentially the secondary OH-group of glycerol rather than primary OH-groups which were almost specifically transgalactosylated by the β-galactosidase. 3. Glycosides with glycerol and trimethylolpropane (TMP) moieties, which were prepared by the transfer reaction, acted as effective substrates for the lipase-catalyzed esterification.