beta-Ureidopropionase of aerobic bacterial origin was purified to homogeneity from Pseudomonas putida IFO 12996. The enzyme shows a broad substrate specificity. In addition to beta-ureidopropionate (Km 3.74 mM, Vmax 4.12 U/mg), gamma-ureido-n-butyrate (Km 11.6 mM, Vmax 19.4 U/mg), and several N-carbamoyl-alpha-amino acids, such as N-carbamoylglycine (Km 0.68 mM, Vmax 9.14 x 10(-2) U/mg), N-carbamoyl-L-alanine (Km 1.56 mM, Vmax 1.00 U/mg), N-carbamoyl-L-serine (Km 75.1 mM, Vmax 3.78 U/mg), and N-carbamoyl-DL-alpha-amino-n-butyrate (Km 2.81 mM, Vmax 1.08 U/mg), are also hydrolyzed. The hydrolysis of N-carbamoyl-alpha-amino acids is strictly L enantiomer specific. N-Formyl-L-alanine and N-acetyl-L-alanine are also hydrolyzed by the enzyme, but the rate of hydrolysis is lower than the rate for N-carbamoyl-L-alanine. The enzyme requires a divalent metal ion, such as Co2+, Ni2+ or Mn2+, for activity, and is significantly affected by sulfhydryl reagents. The enzyme consists of two polypeptide chains with identical relative molecular mass M(r) 45000. The broad substrate specificity and metal ion dependence of the enzyme show that the beta-ureidopropionase of this aerobic bacterium is quite different from the beta-ureidopropionases of mammals and anaerobic bacteria.