Purification and characterization of an endo-beta-(1-->6)-galactanase from Trichoderma viride.
An endo-beta-(1-->6)-galactanase from Onozuka R-10, a commercial cellulase preparation from Trichoderma viride, was purified 57-fold. Apparent Mr values of the purified enzyme, estimated by denaturing gel electrophoresis and gel filtration, were 47,000 and 17,000, respectively. The enzyme was assayed with a galactan from Prototheca zopfii, which has a high proportion of beta-(1-->6)-linked galactosyl residues. It exhibited maximal activity toward the galactan at pH 4.3. The enzyme hydrolyzed specifically beta-(1-->6)-galactooligosaccharides with a degree of polymerization higher than 3 and their acidic derivatives with 4-O-methyl-glucosyluronic or glucosyluronic groups at the nonreducing terminals. The methyl beta-glycoside of beta-(1-->6)-galactohexaose was degraded to reducing galactooligomers with a degree of polymerization 2-5 as the products at the initial stage of hydrolysis, and galactose and galactobiose at the final stage, indicating that the enzyme can be classified as an endo-galactanase. The extent of hydrolysis of the carbohydrate portion of a radish root arabinogalactan-protein (AGP) increased when alpha-L-arabinofuranosyl residues attached to beta-(1-->6)-linked galactosyl side chains of the AGP were removed in advance. The enzyme released galactose, beta-(1-->6)-galactobiose, and 4-O-methyl-beta-glucuronosyl-(1-->6)-galactose as major hydrolysis products when allowed to act exhaustively on the modified AGP.
Okemoto
Kazuo
K
Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, 255 Shimo-okubo, 338-8570, Saitama, Japan.
Uekita
Takamasa
T
Tsumuraya
Yoichi
Y
Hashimoto
Yohichi
Y
Kasama
Takeshi
T
D005656:Fungal Proteins; D005685:Galactans / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008970:Molecular Weight; D013379:Substrate Specificity; D014242:Trichoderma / Q000201:enzymology*; D001616:beta-Galactosidase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
D005656:Fungal Proteins; D005685:Galactans; C478178:endo-beta-(1-6)-galactanase; D001616:beta-Galactosidase