The arginine decarboxylase activities in the same extracts ranged between nanomoles per hour per gram fresh weight being lowest in the borages and highest in oat and barley. In extracts from the youngest leaves of Avena sativa, Hordeum vulgare, Zea Mays, Pisum sativum, Phaseolus vulgaris, Lactuca sativa, and four pyrrolizidine alkaloid-bearing species of Heliotropium, the activities of ornithine decarboxylase, close to Vmax, ranged between traces and 1.5 nanomoles per hour per gram fresh weight when based on putrescine formed during incubation with labeled ornithine.

Addition of aminoguanidine was needed to suppress oxidative degradation of putrescine and agmatine during incubation of extracts from pea, bean, lettuce, Heliotropium angiospermum, and Heliotropium indicum.Īctivities of Arginine and Ornithine Decarboxylases in Various Plant Species 1īirecka, Helena Bitonti, Alan J. In arginine decarboxylase assays, the interfering decarboxylation as well as the interference of arginase were apparent in two species. The in vitro decarboxylase activities found in the borages cannot explain the high accumulation of putrescine-derived pyrrolizidines in their youngest leaves if the pyrrolizidines are produced in situ from arginine and/or ornithine as precursors other possibilities are discussed.In assays of ornithine decarboxylase, an interference of decarboxylation not due to this enzyme was observed in extracts from all species. Agmatine, putrescine, spermidine, and spermine were found in all, diaminopropane in eight, and cadaverine in three species.No correlation was observed between arginine or ornithine decarboxylase level and the levels of total polyamines. alpha-Difluoromethylornithine and alpha-difluoromethylarginine inhibited ornithine and arginine decarboxylases, respectively, in all species. In extracts from the youngest leaves of Avena sativa, Hordeum vulgare, Zea Mays, Pisum sativum, Phaseolus vulgaris, Lactuca sativa, and four pyrrolizidine alkaloid-bearing species of Heliotropium, the activities of ornithine decarboxylase, close to V(max), ranged between traces and 1.5 nanomoles per hour per gram fresh weight when based on putrescine formed during incubation with labeled ornithine. Activities of arginine and ornithine decarboxylases in various plant species.

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