RESUMEN
Allantoate degradation was demonstrated in the extracts of ungerminated seeds and roots, stems and leaves in germinated seedlings of French bean (Phaseolus vulgaris L.). Activity of allantoate-degrading enzyme could only be measured when phenylhydrazine was included in the assay mixture. Partial purification of allantoate-degrading enzyme from seedlings was performed and two fractions with allantoate-degrading enzyme activity were obtained. The molecular mass of the first fraction was over 200 kD and that of the second one was 13.5 kD. The allantoate-degrading enzyme with small molecular weight contained no activity of either ureidoglycolate-degrading enzyme or urease. From the stoichiometry of the reaction catalyzed by the allantoate-degrading enzyme with small molecular weight it followed that the enzyme was allantoate amidohydrolase (EC 3.5.3.9). The optimal pH for the allantoate amidohydrolase was 8.5. Mn(2+) ions were essential for enzymatic activity. Glyoxylate and glycolate strongly inhibited the enzyme activity. The lysine and tryptophan residues were essential to the enzymatic catalysis; thiol group and tyrosyl residues were not involved in the enzyme catalysis.