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Properties of neutral cellobiose dehydrogenase from the ascomycete Chaetomium sp. INBI 2-26(–) and comparison with basidiomycetous cellobiose dehydrogenases

Paper ID Volume ID Publish Year Pages File Format Full-Text
25790 43601 2006 15 PDF Available
Title
Properties of neutral cellobiose dehydrogenase from the ascomycete Chaetomium sp. INBI 2-26(–) and comparison with basidiomycetous cellobiose dehydrogenases
Abstract

The extracellular cellobiose dehydrogenase (CDH) obtained from Chaetomium sp. INBI 2-26(–) has a molecular mass of 95 kDa and an isoelectric point of 5. This novel CDH is highly specific for the oxidation of cellobiose (Km,app 4.5 μM) and lactose (Km,app 56 μM). With 2,6-dichloroindophenol (DCIP) and cytochrome c3+ (cyt c3+) as electron acceptors, CDH was most active at pH 6. The turnover number of the enzyme for cellobiose, lactose, DCIP and cyt c3+ was in the range of 9–14 s−1 at 20 °C and pH 6. The UV–visible spectrum revealed the flavohemoprotein nature of the enzyme. The cytochrome b domain of the enzyme was reduced by ascorbate, dithionite, as well as specifically by cellobiose in a wide range of pH. The apparent first order rate constants of the spontaneous re-oxidation of the reduced heme domain were estimated as 0.01 and 0.00039 s−1 at pH 4.5 and 6.5, respectively. The half-inactivation time of CDH at pH 6 and 55 °C was ca. 100 min; the stability at pH 8 and, particularly, pH 4 was remarkably lower. Cellobiose stabilized the enzyme against thermal inactivation, whereas DCIP in turn sensitized the enzyme. The new enzyme revealed low affinity for crystalline cellulose, but was capable of binding onto H3PO4-swollen filter paper. The results show significant differences to already known CDHs and perspectives for several biotechnological applications, where CDH with maximal activity at neutral pH and high affinity for cellobiose and lactose night have some advantages.

Keywords
BSA, bovine serum albumin; CBM, carbohydrate-binding module; CDH, cellobiose dehydrogenase; CDHcs, CDH Chaetomium sp. INBI 2-26(–); CDHpc, CDH Phanerochaete chrysosporium; CDHsr, CDH Sclerotium (Athelia) rolfsii; CPB, citrate–phosphate buffer; cyt c3+, cy
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Properties of neutral cellobiose dehydrogenase from the ascomycete Chaetomium sp. INBI 2-26(–) and comparison with basidiomycetous cellobiose dehydrogenases
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 121, Issue 1, 2 January 2006, Pages 34–48
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering