Inhibition by 1-Aminocyclobutane-1-Carboxylate of the Activity of 1-Aminocyclopropane-1-Carboxylate Oxidase Obtained from Senescing Petals of Carnation (Dianthus caryophyllus L.) Flowers

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We partially purified 1-aminocyclopropane-1-carboxylate (ACC) oxidase from senescing petals of carnation (Dianthus caryophyllus L. cv . Nora) flowers and investigated its general characteristics, and, in particular, the inhibition of its activity by ACC analogs. The enzyme had an optimum pH at 7-7.5 and required Fe^<2+>, ascorbate and NaHCO_3 for its maximal activity. The K_m for ACC was calculated as 111-125 μM in the presence of NaHCO_3. Its M_r was estimated to be 35 and 36 kDa by gel-filtration chromatography on HPLC and SDS-PAGE, respectively, indicating that the enzyme exists in a monomeric form. These properties were in agreement with those reported previously with ACC oxidases from different plant tissues including senescing carnation petals. Among six ACC analogs tested, 1-aminocyclobutane-1-carboxylate (ACBC) inhibited most severely the activity of ACC oxidase from carnation petals. ACBC acted as a competitive inhibitor with the K_i of 20-31 μM. The comparison between the K_m for ACC and the K_i for ACBC indicated that ACBC had an affinity which was ca. 5-fold higher than that of ACC. Whereas ACC inactivated carnation ACC oxidase in a time-dependent manner during incubation, ACBC did not cause the inactivation of the enzyme. Preliminary experiments showed that ACBC and its N-substituted derivatives delayed the onset of senescence in cut carnation flowers.
日本植物生理学会の論文