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Binding and reversibility of Thermobifida fusca Cel5A, Cel6B, and Cel48A and their respective catalytic domains to bacterial microcrystalline cellulose

Authors

  • Hyungil Jung,

    1. Department of Biological and Environmental Engineering, 232 Riley-Robb Hall, Cornell University, Ithaca, New York 14853; telephone: 607-255-2478; fax: 607-255-4080
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  • David B. Wilson,

    1. Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
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  • Larry P. Walker

    Corresponding author
    1. Department of Biological and Environmental Engineering, 232 Riley-Robb Hall, Cornell University, Ithaca, New York 14853; telephone: 607-255-2478; fax: 607-255-4080
    • Department of Biological and Environmental Engineering, 232 Riley-Robb Hall, Cornell University, Ithaca, New York 14853; telephone: 607-255-2478; fax: 607-255-4080
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Abstract

The binding and reversibility of Thermobifida fusca intact Cel5A, Cel5B, and Cel48A and their corresponding catalytic domains (CDs) to bacterial microcrystalline cellulose (BMCC) were studied at 5°C. The binding of the intact cellulases and of corresponding CDs to BMCC was irreversible in all regions: Langmuir binding (region I), interstice penetration (region II), and interstice saturation (region III). The three cellulose binding domains (CBMs) bind reversibly in “region I” although their respective CDs do not. The irreversible binding of these enzymes in the Langmuir region does not satisfy the Langmuir assumption; however, the overall fit of the Interstice Saturation model, which includes binding in MBCC interstices as well as on the freely accessible surface (Jung et al., 2002a) is good. The main limitation of the model is that it does not explicitly address a mechanism for forming the enzyme-substrate complex within the active site of the CDs. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 151–159, 2003.

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