Diamine oxidation and alkaloid production in transformed root cultures of Nicotiana tabacum

Abstract

Cadaverine, putrescine and N-methylputrescine were all oxidized by extracts of transformed roots of Nicotiana tabacum, the apparent K m values being, respectively, 2.75, 0.35 and 0.08 mM and the relative maximal oxidation rates, 100, 48 and 34%. For the same substrates, partially purified pea seedling diamine oxidase (DAO, EC 1.4.3.6) gave apparent K m values of 0.026, 0.040 and 0.046 mM, with relative maximal activities of 100, 65 and 65% respectively. For the Nicotiana extract, with equimolar substrate concentrations (1 and 0.1 mM), N-methylputrescine inhibited the oxidation of both cadaverine and putrescine, whereas the converse inhibitions did not occur. N-Methylputrescine (1 mM) caused only a modest stimulation of nicotine and nornicotine production when fed to transformed root cultures of N. tabacum, which was inhibited by equimolar cadaverine. Conversely, N-methylputrescine diminished the stimulation of anabasine production by cadaverine.