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Multiple fungal enzymes possess cysteine synthase activity in vitro.

Abstract
We present evidence that there are at least three Aspergillus nidulans enzymes which catalyze in vitro the reaction of O-acetylserine (OAS) with sulfide forming cysteine. This activity is shared by cysteine synthase (CS) encoded by the cysB gene, homocysteine synthase encoded by cysD and by at least one more enzyme. Moreover, arginine, histidine or proline starvation leads to derepression of CS activity even in the cysB,cysD double mutant strains, while neither cysB nor cysD gene transcription is derepressed by amino acid starvation. Using a cpcA mutant, we show that starvation-inducible CS activity is under control of cross-pathway regulation. We identify CysF as a putative CS in A. nidulans. However, cysF gene transcription is not elevated by amino acid starvation. Therefore, it seems that there exists yet another enzyme, thus far unidentified, which possesses CS activity. Using mutants impaired during various steps of cysteine synthesis we prove that the cysB-encoded enzyme is the only CS of physiological importance in the studied fungus. Similar results were obtained with Schizosaccharomyces pombe mutant strains impaired in cysteine synthesis, indicating that the presence of multiple enzymes with in vitro CS activity may be a common feature of many fungal species.
AuthorsJerzy Brzywczy, Renata Natorff, Marzena Sieńko, Andrzej Paszewski
JournalResearch in microbiology (Res Microbiol) Vol. 158 Issue 5 Pg. 428-36 (Jun 2007) ISSN: 0923-2508 [Print] France
PMID17482430 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Sulfates
  • Serine
  • Histidine
  • Arginine
  • Proline
  • Cysteine Synthase
  • O-acetylhomoserine (thiol)-lyase
  • Carbon-Oxygen Lyases
  • O-acetylserine
  • Cysteine
Topics
  • Arginine (metabolism)
  • Aspergillus nidulans (enzymology, genetics, metabolism)
  • Blotting, Northern
  • Carbon-Oxygen Lyases (genetics, metabolism)
  • Catalysis
  • Cysteine (metabolism)
  • Cysteine Synthase (genetics, metabolism)
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Fungal
  • Histidine (metabolism)
  • Models, Biological
  • Mutation
  • Phylogeny
  • Proline (metabolism)
  • Serine (analogs & derivatives, metabolism)
  • Sulfates (metabolism)

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