Characterisation of Fe-containing nitrile hydratases in Rhodococcus strains isolated from soil

Detection of genes encoding α- and β-subunits of Fe-containing nitrile hydratases was fulfilled among aldoxime- and nitrile-utilizing microorganisms isolated from the samples of natural and anthropogenically contaminated soils. The occurrence of enzyme genes did not depend on substrate where the bacteria were isolated (p=0.73). High homology of nha and nhb to well-known nitrile hydratase sequences from GenBank database (from 84 to 99%) was demonstrated. Gene sequencing did not reveal mutations in sites encoding enzyme active centres. The predominance of substitutions was noted among strains isolated from contaminated soil samples (66.7% for α-subunit and 70.0% for β-subunit). Obtained amino acid sequences of enzymes in soil isolates contained both typical for Rhodococcus and unique substitutions of amino acid residues. Radical amino acid substitution of tyrosine for serine in 85 site of a-subunit was demonstrated in strain R. erythropolis B4-4 isolated from acrylamide-contaminated soil.