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UniProt functional annotation for Q9XBQ3 | ||
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| UniProt code: Q9XBQ3. |
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| Organism: | |
Geobacillus stearothermophilus (Bacillus stearothermophilus). |
| Taxonomy: | |
Bacteria; Firmicutes; Bacilli; Bacillales; Bacillaceae; Geobacillus. |
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| Function: | |
Involved in the degradation of arabinan and is a key enzyme in the complete degradation of the plant cell wall. Catalyzes the cleavage of terminal alpha-(1->5)-arabinofuranosyl bonds in different hemicellulosic homopolysaccharides (branched and debranched arabinans). It acts preferentially on aryl-alpha-L-arabinofuranosides, and is much less effective on aryl-beta-D-xylopyranosides. {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}. |
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| Catalytic activity: | |
Reaction=Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides.; EC=3.2.1.55; Evidence={ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232}; |
| Activity regulation: | |
Strongly inhibited by Hg(2+). {ECO:0000269|PubMed:7887599}. |
| Biophysicochemical properties: | |
Kinetic parameters: KM=0.35 mM for 2,5-dinitro-arabinofuranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=0.42 mM for p-nitrophenyl alpha-L-arabinofuranoside (pNP-Araf) (at 60 degrees Celsius and at pH 6) {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=0.53 mM for 3,4-dinitro-arabinofuranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=0.65 mM for 4-nitro-arabinofuranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=4.4 mM for 3,4-dinitro-xylopyranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=8 mM for 2,5-dinitro-xylopyranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; KM=15.3 mM for 2-nitro-xylopyranosyl {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; Vmax=749 umol/min/mg enzyme (at 60 degrees Celsius and at pH 6) {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; Note=Apparently, AbfA can accommodate xylopyranose in the active site, but without the necessary distortion required for the efficient catalysis of six-membered rings. This explains in part its lower specificity towards the xylopyranosidic substrates (PubMed:14517232).; pH dependence: Optimum pH is 5.5-6.0. {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; Temperature dependence: Optimum temperature is 70 degrees Celsius. {ECO:0000269|PubMed:11943144, ECO:0000269|PubMed:12221104, ECO:0000269|PubMed:14517232, ECO:0000269|PubMed:7887599}; |
| Pathway: | |
Glycan metabolism; L-arabinan degradation. |
| Subunit: | |
Homohexamer; trimer of dimers. {ECO:0000305|PubMed:12777810, ECO:0000305|PubMed:14517232, ECO:0000305|PubMed:7887599}. |
| Subcellular location: | |
Cytoplasm {ECO:0000250}. |
| Induction: | |
Transcription is repressed by glucose and by the binding of AraR to the operon promoter. L-arabinose acts as an inducer by inhibiting the binding of AraR to the DNA, thus allowing expression of the gene (Probable). {ECO:0000305|PubMed:7887599}. |
| Similarity: | |
Belongs to the glycosyl hydrolase 51 family. {ECO:0000305}. |
Annotations taken from UniProtKB at the EBI.