Cloning and properties of a cyanide hydratase gene from the phytopathogenic fungus Gloeocercospora sorghi.

The Cht gene encoding cyanide hydratase (CHT, EC 4.2.1.66), which detoxifies HCN and is thought to be important in fungal infection of cyanogenic plants, has been cloned from the phytopathogenic fungus Gloeocercospora sorghi. The gene was isolated by screening an expression library of G. sorghi using a CHT-specific antibody and using one of the positive cDNA clones as a probe in Southern hybridization to identify a 3.1 kb PstI genomic fragment. This PstI fragment expressed CHT activity when transformed into Aspergillus nidulans, a fungus that normally lacks CHT activity. Sequence analysis identified a single open reading frame of 1,107 base pairs which encodes a polypeptide of 40,904 daltons. The deduced amino acid sequence of CHT shares 36.5% identity to a nitrilase from the bacterium Klebsiella pneumoniae subsp. ozaenae.