Plants synthesize ethanolamine by direct decarboxylation of serine using a pyridoxal phosphate enzyme

J Biol Chem. 2001 Sep 21;276(38):35523-9. doi: 10.1074/jbc.M106038200. Epub 2001 Jul 18.


The established pathways from serine to ethanolamine are indirect and involve decarboxylation of phosphatidylserine. Here we show that plants can decarboxylate serine directly. Using a radioassay based on ethanolamine (Etn) formation, pyridoxal 5'-phosphate-dependent l-serine decarboxylase (SDC) activity was readily detected in soluble extracts from leaves of diverse species, including spinach, Arabidopsis, and rapeseed. A putative Arabidopsis SDC cDNA was identified by searching GenBank for sequences homologous to other amino acid decarboxylases and shown by expression in Escherichia coli to encode a soluble protein with SDC activity. This cDNA was further authenticated by complementing the Etn requirement of a yeast psd1 psd2 mutant. In a parallel approach, a cDNA was isolated from a rapeseed library by its ability to complement the Etn requirement of a yeast cho1 mutant and shown by expression in E. coli to specify SDC. The deduced Arabidopsis and rapeseed SDC polypeptides are 90% identical, lack obvious targeting signals, and belong to amino acid decarboxylase group II. Recombinant Arabidopsis SDC was shown to exist as a tetramer and to contain pyridoxal 5'-phosphate. It does not attack d-serine, l-phosphoserine, other l-amino acids, or phosphatidylserine and is not inhibited by Etn, choline, or their phosphoesters. As a soluble, pyridoxal 5'-phosphate enzyme, SDC contrasts sharply with phosphatidylserine decarboxylases, which are membrane proteins that have a pyruvoyl cofactor.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology
  • Arabidopsis / metabolism*
  • Carboxy-Lyases / chemistry
  • Carboxy-Lyases / genetics
  • Carboxy-Lyases / metabolism*
  • Cloning, Molecular
  • DNA, Complementary
  • Ethanolamine / metabolism*
  • Genetic Complementation Test
  • Molecular Sequence Data
  • Plant Leaves / enzymology
  • Plant Leaves / metabolism
  • Pyridoxal Phosphate / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Sequence Homology, Amino Acid
  • Serine / metabolism*


  • DNA, Complementary
  • Recombinant Proteins
  • Serine
  • Ethanolamine
  • Pyridoxal Phosphate
  • Carboxy-Lyases
  • L-serine decarboxylase

Associated data

  • GENBANK/AB014076
  • GENBANK/AF389349