Stability and Folding of Endoglucanase I (CEL7B) from Humicoia Insolens

Daniel Otzen, Martin Schülein

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Cellulases are of economic significance, particularly in the detergent and textile industries, where they are subjected to a wide range of operating conditions affecting their stability. To increase our insight into the properties of this class of enzymes, we have carried out a study of the stability and folding behavior of the 413-residue endoglucanase I (Ce17B) from Humicola insolens. Data from chemical denaturation in guanidinium chloride agree satisfactorily with calorimetric measurements, revealing an optimum stability of ca. 20 kcal mol−1 around pH 7 and a peak half-width of 3 -4 pH units. Stability and activity show very similar pH-profiles, but this is probably fortuitous. Judging from equilibrium m-values (the dependence of the log of the equilibrium unfolding constant on the denaturant concentration), the denatured state becomes significantly more compact outside pH 6–9. Folding and unfolding proceed very slowly with relaxation half times up to 6h. Single- and double-jump kinetic data at pH 7 suggest a folding scheme involving two intermediates with native-like secondary structure but varying degrees of tertiary structure.

TidsskriftBiocatalysis and Biotransformation
Sider (fra-til)469-487
Antal sider19
StatusUdgivet - 1 jan. 2001


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