Arabidopsis polyamine biosynthesis: Absence of ornithine decarboxylase and the mechanism of arginine decarboxylase activity

Colin Hanfrey, Susanne Sommer, Melinda J. Mayer, Daniel Burtin, Anthony J. Michael

Research output: Contribution to journalArticle

186 Scopus citations

Abstract

Unlike other eukaryotes, which can synthesize polyamines only from ornithine, plants possess an additional pathway from arginine. Occasionally non-enzymatic decarboxylation of ornithine could be detected in Arabidopsis extracts; however, we could not detect ornithine decarboxylase (ODC; EC 4. 1.1.17) enzymatic activity or any activity inhibitory to the ODC assay. There are no intact or degraded ODC sequences in the Arabidopsis genome and no ODC expressed sequence tags. Arabidopsis is therefore the only plant and one of only two eukaryotic organisms (the other being the protozoan Trypanosoma cruzi) that have been demonstrated to lack ODC activity. As ODC is a key enzyme in polyamine biosynthesis, Arabidopsis is reliant on the additional arginine decarboxylase (ADC; EC 4.1.1.9) pathway, found only in plants and some bacteria, to synthesize putrescine. By using site-directed mutants of the Arabidopsis ADC1 and heterologous expression in yeast, we show that ADC, like ODC, is a head-to-tail homodimer with two active sites acting in trans across the interface of the dimer. Amino acids K136 and C524 of Arabidopsis ADC1 are essential for activity and participate in separate active sites. Maximal activity of Arabidopsis ADC1 in yeast requires the presence of general protease genes, and it is likely that dimer formation precedes proteolytic processing of the ADC pre-protein monomer.

Original languageEnglish (US)
Pages (from-to)551-560
Number of pages10
JournalPlant Journal
Volume27
Issue number6
DOIs
StatePublished - Oct 23 2001

Keywords

  • Arabidopsis
  • Arginine decarboxylase
  • Ornithine decarboxylase
  • Polyamine

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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