Carboanhydrasen und CO₂-Stoffwechsel

Carbonic anhydrases (CAs) are metalloenzymes that catalyze the interconversion of carbon dioxide and bicarbonate with high efficiency. This reaction is fundamental to biological processes such as respiration, pH homeostasis and CO₂ transport. In fungi, CAs are part of the CO₂-sensing system of pathogens and take part in the regulation of sexual development.
S. macrospora has four CA genes. Three of them, cas1, cas2 and cas3, encode β-class enzymes; the fourth, cas4, encodes an α-class enzyme. We showed that β-CAs play a role in fruiting-body development and ascospore germination. Surprisingly, S. macrosporacan survive in ambient air even without carbonic anhydrases.
To understand how these enzymes work, we solved the crystal structures of two tetrameric β-CAs of S. macrospora and compared the structures of fungal CAs. Together with collaboration partners we characterized the inhibition of CAS1 and CAS2 by sulfonamides and of CAS3 by sulfonamides and anions. We also analyzed the evolution of CAs in fungi. Related work addressed a cyanase that is transcriptionally regulated by arginine and involved in cyanate decomposition.