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Gewählte Publikation:

Sygmund, C; Kracher, D; Scheiblbrandner, S; Zahma, K; Felice, AKG; Harreither, W; Kittl, R; Ludwig, R.
(2012): Characterization of the Two Neurospora crassa Cellobiose Dehydrogenases and Their Connection to Oxidative Cellulose Degradation
APPL ENVIRON MICROB. 2012; 78(17): 6161-6171. FullText FullText_BOKU

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 HA 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 (k(cat) and K-m 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 (NCUO2916) from N. crassa was expressed in P. pastoris. A pH-dependent 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.
Autor/innen der BOKU Wien:
Felice Alfons Konrad
Harreither Wolfgang
Kittl Roman
Kracher Daniel
Ludwig Roland
Scheiblbrandner Stefan
Sygmund Christoph
Zahma Kawah
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