[A dicarboxylate monoamide amidohydrolase (half-amidase) from Alcaligenes eutrophus 112R4]

A dicarboxylate monoamide amidohydrolase (half-amidase) was identified from a cyclicimide-metabolizing microorganism, Alcaligenes eutrophus 112R4. The enzyme catalyzed the hydrolysis of monoamidated dicarboxylates, which were the hydrolyzing products of cyclic imides by imidase, to dicarboxylates and ammonia. The enzyme showed high catalytic activity to succinamic acid, but no obvious activity to aliphatic amides, amino acid amides, N-carbamoyl amino acids and urea was observed. The productions of half-amidase and imidase were correlative in Alcaligenes eutrophus 112R4, in that succinimide and succinamic acid enhanced the expressions of these two enzymes simultaneously, while free ammonia repressed their expressions. Succinate showed regulation effects on either synthesis or activities of half-amidase and imidase. The characteristics of half-amidase were investigated by using the crude extract of recombined E. coli cell. The fact that cobalt ion stimulated the activity of half-amidase by a coefficient of 3.37, implied that half-amidase was probably a metal-binding enzyme.