Allophanate hydrolase of Oleomonas sagaranensis involved in an ATP-dependent degradation pathway specific to urea

The first prokaryotic urea carboxylase has previously been purified and characterized from Oleomonas sagaranensis. As the results indicated the presence of an ATP-dependent urea degradation pathway in Bacteria, the characterization of the second component of this pathway, allophanate hydrolase, was carried out. The gene encoding allophanate hydrolase was found adjacent to the urea carboxylase gene. The purified, recombinant enzyme exhibited ammonia-generating activity towards allophanate, and, together with urea carboxylase, efficiently produced ammonia from urea in an ATP-dependent manner. The substrate specificity of the enzyme was strict, and analogs of allophanate were not hydrolyzed. Moreover, although the urea carboxylase exhibited carboxylase activity towards urea, acetamide, and formamide, ammonia-releasing activity of the two enzymes combined was detected only towards urea, indicating that the pathway was specific for urea degradation.