Characterization of the two Neurospora crassa cellobiose dehydrogenases and their connection to oxidative cellulose degradation

Christoph Sygmund, Daniel Kracher, Stefan Scheiblbrandner, Kawah Zahma, Alfons K.G. Felice, Wolfgang Harreither, Roman Kittl, Roland Ludwig*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The genome of Neurospora crassa encodes two different cellobiose dehydrogenases (CDHs) with a sequence identity of only 53%. So far, only CDH IIA, which is induced during growth on cellulose and features a C-terminal carbohydrate binding module (CBM), was detected in the secretome of N. crassa and preliminarily characterized. CDH IIB is not significantly upregulated during growth on cellulosic material and lacks a CBM. Since CDH IIB could not be identified in the secretome, both CDHs were recombinantly produced in Pichia pastoris. With the cytochrome domain-dependent one-electron acceptor cytochrome c, CDH IIA has a narrower and more acidic pH optimum than CDH IIB. Interestingly, the catalytic efficiencies of both CDHs for carbohydrates are rather similar, but CDH IIA exhibits 4- to 5-times-higher apparent catalytic constants (kcat and Km values) than CDH IIB for most tested carbohydrates. A third major difference is the 65-mV-lower redox potential of the heme b cofactor in the cytochrome domain of CDH IIA than CDH IIB. To study the interaction with a member of the glycoside hydrolase 61 family, the copper-dependent polysaccharide monooxygenase GH61-3 (NCU02916) from N. crassa was expressed in P. pastoris. A pHdependent electron transfer from both CDHs via their cytochrome domains to GH61-3 was observed. The different properties of CDH IIA and CDH IIB and their effect on interactions with GH61-3 are discussed in regard to the proposed in vivo function of the CDH/GH61 enzyme system in oxidative cellulose hydrolysis.

Original languageEnglish
Pages (from-to)6161-6171
Number of pages11
JournalApplied and Environmental Microbiology
Volume78
Issue number17
DOIs
Publication statusPublished - Sep 2012
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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