A modular xylanase containing a novel non-catalytic xylan-specific binding domain
| Autor: | S J Millward-Sadler, Gary W. Black, Judith I. Laurie, Harry J. Gilbert, Geoffrey P. Hazlewood |
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| Rok vydání: | 1995 |
| Předmět: |
animal structures
Recombinant Fusion Proteins Molecular Sequence Data Gram-Positive Asporogenous Rods Polysaccharide digestive system Biochemistry Catalysis Chromatography Affinity Substrate Specificity chemistry.chemical_compound Bacterial Proteins Polysaccharides Cellulose Molecular Biology chemistry.chemical_classification Binding Sites Endo-1 4-beta Xylanases Base Sequence beta-Glucosidase Substrate (chemistry) Xylan binding Cell Biology Xylan Peptide Fragments digestive system diseases Protein Structure Tertiary Xylosidases surgical procedures operative Enzyme chemistry Xylanase Xylans Research Article Binding domain |
| Zdroj: | Biochemical Journal. 307:191-195 |
| ISSN: | 1470-8728 0264-6021 |
| Popis: | Xylanase D (XYLD) from Cellulomonas fimi contains a C-terminal cellulose-binding domain (CBD) and an internal domain that exhibits 65% sequence identity with the C-terminal CBD. Full-length XYLD binds to both cellulose and xylan. Deletion of the C-terminal CBD from XYLD abolishes the capacity of the enzyme to bind to cellulose, although the truncated xylanase retains its xylan-binding properties. A derivative of XYLD lacking both the C-terminal CBD and the internal CBD homologue did not bind to either cellulose or xylan. A fusion protein consisting of the XYLD internal CBD homologue linked to the C-terminus of glutathione S-transferase (GST) bound to xylan, but not to cellulose, while GST bound to neither of the polysaccharides. The Km and specific activity of full-length XYLD and truncated derivatives of the enzyme lacking the C-terminal CBD (XYLDcbd), and both the CBD and the internal CBD homologue (XYLDcd), were determined with soluble and insoluble xylan as the substrates. The data showed that the specific activities of the three enzymes were similar for both substrates, as were the Km values for soluble substrate. However, the Km values of XYLD and XYLDcbd for insoluble xylan were significantly lower than the Km of XYLDcd. Overall, these data indicate that the internal CBD homologue in XYLD constitutes a discrete xylan-binding domain which influences the affinity of the enzyme for insoluble xylan but does not directly affect the catalytic activity of the xylanase. The rationale for the evolution of this domain is discussed. |
| Databáze: | OpenAIRE |
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