In this study we demonstrate that the abp gene in Geobacillus stearothermophilus T-6 encodes a family 27 glycoside hydrolase β-l-arabinopyranosidase. The catalytic constants towards the chromogenic substrate pNP-β-l-arabinopyranoside were 0.8 ± 0.1 mM, 6.6 ± 0.3 s -1, and 8.2 ± 0.3 s -1 mM -1 for K m, k cat and k cat/K m, respectively. 13C NMR spectroscopy unequivocally showed that Abp is capable of removing β-l-arabinopyranose residues from the natural arabino- polysaccharide, larch arabinogalactan. Most family 27 enzymes are active on galactose and contain a conserved Asp residue, whereas in Abp this residue is Ile67, which shifts the specificity of the enzyme towards arabinopyranoside. Crown
Bibliographical noteFunding Information:
This work was supported by the Israel Science Foundation Grant 500/10 (to Y. S.), United States-Israel Binational Science Foundation (BSF; Jerusalem, Israel) Grant 96 178 (to Y. S.), the I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation (grant No 152/11), the Ministry of Environmental Protection, Grand Technion Energy Program (GTEP) and the Helmsley Charity Fund.
- C NMR
- Glycoside hydrolase family 27
- Larch arabinogalactan
- Sugar beet arabinan