Tracer studies with C-13-labeled carbohydrates in cultured plant cells. Retrobiosynthetic analysis of chelidonic acid biosynthesis

The biosynthesis of chelidonic acid was studied in cell suspension cultures of Leucojum aestivum. Cell cultures were supplied with [U-C-13(6)]glucose, [1-C-13]glucose or [U-C-13(5)]ribose/ribulose in standard medium containin g unlabeled glucose. C-13 labeling patterns of amino acids obtained by hydr olysis of biomass were determined by NMR spectroscopy and compared to the l abeling pattern of chelidonic acid. The data document the incorporation of a contiguous 4-carbon fragment derived from the pentose phosphate pool into chelidonic acid. This suggests a biosynthetic pathway involving the conden sation of phosphoenolpyruvate with a pentose phosphate followed by dehydrat ion, dehydrogenation, ring closure and decarboxylation conducive to the los s of C-5 of the pentose precursor. (C) 2001 Elsevier Science Ltd. All right s reserved.