Journal
FUNGAL GENETICS AND BIOLOGY
Volume 45, Issue 11, Pages 1458-1469Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.fgb.2008.08.005
Keywords
Cyanase; Cyanate; Bicarbonate; Carbon dioxide; Ammonium; Arginine biosynthesis; Sordaria macrospora
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Funding
- Ruhr-Universiry of Bochum
- Georg-August University of Gottingen
- Deutsche Forschungsgemeinschaft [PO523/3-2]
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Cyanase degrades toxic cyanate to NH3 and CO2 in a bicarbonate-dependent reaction. High concentrations of cyanate are fairly toxic to organisms. Here, we characterize a eukaryotic cyanase for the first time. We have isolated the cyn1 gene encoding a cyanase from the filamentous ascomycete Sordaria macrospora and functionally characterized the cyn1 product after heterologous expression in Escherichia coli. Site-directed mutagenesis confirmed a predicted catalytic centre of three conserved amino-acids. A Delta cyn1 knockout in S. macrospora was totally devoid of cyanase activity and showed an increased sensitivity to exogenously supplied cyanate in an arginine-depleted medium, defects in ascospore germination, but no other obvious morphological phenotype. By means of real-time PCR we have demonstrated that the transcriptional level of cyn1 is markedly elevated in the presence of cyanate and down-regulated by addition of arginine. The putative functions of cyanase in fungi are discussed. (c) 2008 Elsevier Inc. All rights reserved.
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