An enzyme hydrolyzing the condensation products of urea and formaldehyde (ureaform) was purified and characterized from a bacterium isolated from soil and described as Ochrobactrum anthropi UF4. The enzyme designated as methylenediurea amidinohydrolase (methylenediurea deiminase) hydrolyzed ureaform condensation products of different length (methylenediurea, dimethylenetriurea, trimethylenetetraurea) to ammonium, formaldehyde, and urea at molar ratios of 2:1:1 (methylenediurea), 4:2:1 (dimethylenetriurea), and 6:3:1 (trimethylenetetraurea). Two other substrates, ureidoglycolate and allantoate, were also hydrolyzed, yielding glyoxylate and urea (ureidoglycolate) and glyoxylate, urea, and ammonium (allantoate), respectively. The molecular mass of the enzyme was determined by size exclusion chromatography to be 140 ± 25 kDa; the enzyme was composed of identical subunits of 38 ± 5 kDa, indicating that the native enzyme has a tetrameric structure. Growth of the bacterium in the presence of ureaform specifically induced the methylenediurea deiminase and no complete repression of enzyme synthesis by ammonium was observed.Key words: ureaformaldehyde, methylenediurea deiminase, fertilizer, Ochrobactrum anthropi.

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A new enzyme (isobutylidenediurea amidinohydrolase) catalyzing the hydrolysis of isobutylidenediurea (a condensation product of urea and isobutyraldehyde widely used as a slow-release nitrogeneous fertilizer) was characterized from a strain of Rhodococcus erythropolis. The enzyme was purified 1,250-fold to apparent homogeneity and shown to hydrolyze the fertilizer to urea and isobutyraldehyde at a molar ratio of 2: 1. No activity was observed with ureido- or other structurally related compounds. Its molecular mass was determined by native polyacrylamide gelelectrophoresis and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry to be 15 kDa (+/-2 kDa) and 16.4 kDa, respectively. Growth of the bacterium in the presence of isobutylidenediurea led to an increased expression of the constitutively synthetized enzyme.

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