INHIBITORS OF TWO ENZYMES WHICH METABOLIZE CYTOKININS

Article abstract of DOI:10.1016/S0031-9422(00)85471-0

Compounds which inhibit the natural metabolic inactivation of cytokinins are cosiderable physiological significance.In this study, inhibitors have been found for two enzymes which form glucose and alanine conjugates of cytokinin bases, namely, cytokinin 7-glucosyltransferase and β-(9-cytokinin)alanine synthase.The most effective inhibitors found for the former enzyme were the cytokinin analogues 3-methyl-7-n-pentylaminopyrazolo<4,3-d>pyrimidine, which acted competitively (K_i 22 μM), and the diaminopurine, 6-benzylamino-2-(2-hydroxyethylamino)-9-methylpurine (K_i 3.3 μM).However these compounds were ineffective as inhibitors of the cytokinin-alanine sythase which was inhibited competitively by IAA (K_i 70 μM) and related compounds, especially 5,7-dichloro-IAA (K_i 0.4 μM).Certain urea derivatives were moderately effective inhibitors of the enzymes (K_i ca 100 μM). Key Word Index - Cytokinins; metabolism; cytokinin 7-glucosyltransferase; β-(9-cytokinin)alanine synthase; N⁶-substituted adenines; auxins; indoleacetic acid.