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.
- Gal2- Gal3 and Gal4
β-1,4-galactobiose, -triose and -tetraose
Endo-1,4-β-galactanase, arabinogalactan 4-β-d-galactanohydrolase (EC 188.8.131.52)
endo-1,3-β-galactanase. arabinogalactan 3-β-d-galactanohydrolase (EC 184.108.40.206)
β-galactosidase, β-d-galactoside galactohydrolase (EC 220.127.116.11)
α-arabinosidase, α-l-arabinofuranoside arabinofuranohydrolase (EC 18.104.22.168)
β-amylase, 1,4-α-d-glucan maltohydrolase (EC 22.214.171.124)