title: Biosynthesis of the pyrimidinyl amino acid lathyrine by Lathyrus tingitanus L.
abstract: The biosynthesis of the pyrimidinyl amino acid lathyrine by seedlings of Lathyrus tingitanus L. was shown to be stimulated by uracil. [6(-14)C]Orotate, [2(-14)C]uracil and [3(-14)C]serine were incorporated into lathyrine; the incorporation of [6(-14)C]orotate was substantially decreased in the presence of uracil. Chemical degradation to locate the 14C incorporated from labelled precursors showed that 90% of the radioactivity incorporated into lathyrine from [3(-14)C]serine could be recovered in the alanine side chain. Over 80% of the radioactivity incorporated from [2(-14)C]uracil was shown to be located in C-2 of lathyrine. It is concluded that under the conditions studied, lathyrine arises from a preformed pyrimidine arising via the orotate pathway. Paradoxically, it was also possible to confirm previous reports that radioactivity from L-[guanidino-14C]homoarginine is incorporated into lathyrine and gamma-hydroxyhomoarginine. However, as homoarginine and gamma-hydroxyhomoarginine are also both labelled by [2(-14)C]uracil, it is suggested that they are products of the ring-opening of lathyrine and that reversibility of this process accounts, at least in part, for their observed experimental incorporation into lathyrine.
mesh_terms: D000599:Amino Acids, Diamino / Q000096:biosynthesis*; D006709:Homoarginine / Q000031:analogs & derivatives / Q000378:metabolism; D009963:Orotic Acid / Q000378:metabolism; D010944:Plants / Q000187:drug effects / Q000378:metabolism*; D011743:Pyrimidines / Q000096:biosynthesis*; D014498:Uracil / Q000494:pharmacology
chemical_list: D000599:Amino Acids, Diamino; D011743:Pyrimidines; D006709:Homoarginine; C015277:hydroxyhomoarginine; D014498:Uracil; D009963:Orotic Acid