Molecular cloning and expression of a novel catechol 2,3-dioxygenase gene from the benzoate meta-cleavage pathway in Azotobacter vinelandii

Azotobacter vinelandii strain 206 degrades benzoate via the meta-cleavage pathway. In a genomic library derived from this organism a clone was obtained which carried and expressed the gene for the third enzyme in this pathway, catechol 2,3-dioxygenase (EC 1.13.11.2), on a 5.9 kb SalI restriction fragment. The structural gene was more precisely mapped on an internal 1.6 kb EcoRI fragment which, after insertion into expression vectors, directed the synthesis of a 33 kDa polypeptide. The gene showed very little or no homology with isofunctional genes derived from Pseudomonas. Comprehensive substrate specificity analysis showed significant differences between the specific activities obtained from the cloned gene product and extracts derived from Azotobacter itself.