Agmatine deiminase was purified to homogeneity from cucumber seedlings. The purification procedures included treatment With DE52, ammonium sulfate precipitation, DE52 column chromatography, Superdex 200 column chromatography, and agmatine(CNBr)-diaminohexane-CNBr-activated-Sepharose 413 column chromatography. The purified agmatine deiminase exhibited a specific activity of 242 nkat/mg protein at 30degreesC, pH 7.0, with a yield of 33%. The molecular mass of the native enzyme was 67 kDa, as estimated by Superdex 200 column chromatography. On the other hand, SDS-PAGE showed that the molecular masses of the subunits with 1% SDS and 5% of 2-mercaptoethanol treatment and with additional N-glycosidase F treatment were 47 and 36 kDa, respectively. These results suggest that agmatine deiminase from cucumber is a glycoprotein. The K-m of the enzyme for agmatine was 16 muM and arcaine was a potent competitive inhibitor of the enzyme, with a K-i of 7.1 muM. The enzyme was stable for 2 months at 4degreesC. The enzyme does not have putrescine synthase activity or the activities of its components ornithine and putrescine transcarbamylase. The characteristics of the enzyme purified from cucumber were like those of the enzyme from maize. These results indicate that agmatine deiminase is distinctly different from putrescine synthase in higher plants. (C) 2003 Elsevier Science (USA). All rights reserved.