Pyrimidine primary and secondary metabolism in plants

• Main Author: Turan, Y.
• Published: Swansea University 1995
• Subjects: 572.2
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639271

In this study, the biosynthesis of albizziine has been elucidated, and a direct precursor relationship shown to exist between uracil and albizziine. This was confirmed by the demonstration that [2-<SUP>14</SUP>C]uracil specifically labels C-5 of albizziine. It is concluded that the biosynthetic sequence involves the hydroxylation of uracil to isobarbituric acid, then amination to 5-aminouracil, followed by hydrogenation and ring-opening, to yield albizziine. 2,3-Diaminopropanoic acid was shown to be formed from albizziine by the action of β-ureidopropionase. Thus, the formation of albizziine and 2,3-diaminopropanoic acid represents a further aspect of the interfacing of pyrimidine primary and secondary metabolism through uracil. Lathyrine was shown to be catabolyzed in <I>Lathyrus tingitanus</I> to yield the non-protein amino acid 4-hydroxyhomoarginine, and it was thus confirmed that 4-hydroxyhomoarginine is a catabolite rather than a precursor of lathyrine. 2-Amino-4-carboxypyrimidine, the immediate precursor of the lathyrine ring-system, was shown to be synthesized enzymically from uracil. The relative amount of exogenously supplied uracil diverted into production of the isomeric pyrimidinyl amino acids willardiine and isowillardiine in <I>Pisum sativum</I>, and also that diverted into the production of the pyrimidine amino acid lathyrine in <I>Lathyrus tingitanus</I> was determined. Uracil was shown to have a pronounced inhibitory effect on the germination and growth of <I>Phaseolus aureus</I> and <I>Glycine max</I>. As these plants do not produce pyrimidine-derived secondary products, this observation is consistent with the view that production of such compounds is a detoxification mechanism for bioactive pyrimidines.