METABOLISM OF ARGININE AND ORNITHINE IN SUSPENSION-CULTURED CELLS ANDASEPTIC ROOTS OF INTACT PLANTS OF ATROPA-BELLADONNA

Suspension-cultured cells and aseptically cultured roots of intact pla nts of Atropa belladonna L. removed tropane alkaloid precursors argini ne (Arg) and ornithine (0m) at nearly an equal rate from the feeding m edium. A great part of Arg- and Orn-derived C-14-label was found in et hanol-insoluble compounds, mostly in proteins already after 2 h feedin g. Ethanol-soluble label in the roots was found mainly in amino acids (e.g. glutamine, Gln) after 2 h feeding, and after 20 h also in some i ntermediates of the urea cycle (e.g. argininosuccinate).In suspension cultures, subculturing of the initiation callus decreased both the upt ake of the basic amino acids tested and their binding on to the apopla stic space. After 20 h feeding with Arg more label was found in organi c acids in stationary phase suspension cultures with repressed alkaloi d synthesis than in roots producing alkaloids. The growth phase and pa ssage number also affected into which amino acids the label was incorp orated. When the initiation callus was young (the 3rd passage), the in termediates of the urea cycle were actively labelled, but when the ini tiation callus was older (the 8th passage) and the suspension formed r oots, especially Gln was labelled. Only traces of sigma-N-methylornith ine were detected in feeding experiments with Orn and Arg. Considerabl e arginase activity with a high pH optimum was observed in cell suspen sions and roots of A. belladonna.