Deactivation of formate dehydrogenase (FDH) in solution and at gas-liquid interfaces |
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Authors: | Bommarius Andreas S Karau Andreas |
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Institution: | Research, Development and Appl. Technology Fine Chemicals, Degussa AG, P.O. Box 1345, D-63403 Hanau, Germany. andreas.bommarius@chbe.gatech.edu |
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Abstract: | Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas-liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, E](t)/E](0), and residual protein were found to scale proportionally with gas-liquid surface area in the bubble column, verifying a surface-driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first-order deactivation constant k(d) correlates well with the Jones-Dole coefficient B but not well with the surface tension increment deltasigma of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects. |
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