Purification and characterization of an exo-1,4-β-galactanase from a strain of Bacillus subtilis

Authors


Correspondence to H. Nakano, Osaka Municipal Technical Institute, 6-50 Morinomiya 1-chome, Jyoto-ku, Osaka, Japan 536

Abstract

An arabinogalactan 4-β-d-galactanohydrolase was purified to a homogeneous state from the culture filtrate of a strain of Bacillus subtilis. The enzyme have a molecular mass of 36 kDa and an isoelectric point of pH 7.9. The enzyme is most active at around pH 6.5–7 and at 60°C, and is stable between pH 6–10 and below 55°C. Hg2+ and Cu2+ inhibit the activity. The enzyme hydrolyze soybean arabinogalactan which contains β-1,4-galactosidic linkages in its main chain structure, but not other polysaccharides with β-1,3-galactosidic linkages. The hydrolysis products from soybean arabinogalactan are predominantly galactobiose with a small amount of galactotetraose. The enzyme is an exo-enzyme and the ability to transfer galactobiose to other galactobiose molecules is indicated by the formation of galactotetraose.

Abbreviations
SAG

soybean arabinogalactan

Gal2- Gal3 and Gal4

β-1,4-galactobiose, -triose and -tetraose

NpGal

o-nitrophenyl-β-galactoside

Np

o-nitrophenol

Gal2-Np

o-nitrophenyl-β-galacto-bioside

Enzymes
 

Endo-1,4-β-galactanase, arabinogalactan 4-β-d-galactanohydrolase (EC 3.2.1.89)

 

endo-1,3-β-galactanase. arabinogalactan 3-β-d-galactanohydrolase (EC 3.2.1.90)

 

β-galactosidase, β-d-galactoside galactohydrolase (EC 3.2.1.23)

 

α-arabinosidase, α-l-arabinofuranoside arabinofuranohydrolase (EC 3.2.1.55)

 

β-amylase, 1,4-α-d-glucan maltohydrolase (EC 3.2.1.2)

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