Biosynthetic pathway of mycosporines (mycosporine-like amino acids) in the cyanobacterium Chlorogloeopsis sp. strain PCC 6912

Anne Portwich, Ferran Garcia-Pichel

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Abstract

We used metabolic inhibitors and radiolabelled tracers to investigate the biosynthetic pathway for mycosporines (mycosporine-like amino acids) in the facultatively heterotrophic cyanobacterium (blue-green alga) Chlorogloeopsis sp. strain PCC 6912. 14C-pyruvate was taken up and resulted in labelling of the core cyclohexenone, whereas feeding with 14C-acetate did not label cyclohexenone, in spite of strong cellular uptake. In addition, mycosporine synthesis was depressed in the presence of externally administered tyrosine (5 mM), a known feedback inhibitor of the shikimic acid pathway in cyanobacteria. We thus conclude that the mycosporine core cyclohexenone in cyanobacteria is derived from the shikimate pathway, as has been suggested for eukaryotic organisms. The use of other putative inhibitors did not yield clear evidence, but cerulenin was found to be a potent inhibitor of mycosporine biosynthesis. Using radiolabelled amino acids, we determined the origin of the variable mycosporine amino acidic side chains. We detected specific incorporation of 14C-glycine and 14C-serine into the corresponding side chains of mycosporine-glycine and shinorine, demonstrating that free amino acids are their direct precursors. A pulse-chase experiment using 14C-glycine demonstrated that the monosubstituted mycosporine, mycosporine-glycine, is a direct metabolic precursor of the bisubstituted mycosporine, shinorine. These results support the idea that the large diversity of mycosporine molecules found in nature is produced by variations in late biosynthetic steps, which add amino-moieties to the core. In particular, we can postulate the existence of a shinorine synthase catalysing the condensation of mycosporine-glycine and serine in this cyanobacterium.

Original languageEnglish (US)
Pages (from-to)384-392
Number of pages9
JournalPhycologia
Volume42
Issue number4
StatePublished - Jul 2003

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Chlorogloeopsis
glycine (amino acid)
biochemical pathways
Cyanobacteria
cyanobacterium
amino acid
inhibitor
amino acids
serine
shikimate pathway
shikimic acid
metabolic inhibitors
free amino acids
tyrosine
condensation
tracer techniques
acetate
tracer
acetates
biosynthesis

ASJC Scopus subject areas

  • Aquatic Science
  • Plant Science

Cite this

Biosynthetic pathway of mycosporines (mycosporine-like amino acids) in the cyanobacterium Chlorogloeopsis sp. strain PCC 6912. / Portwich, Anne; Garcia-Pichel, Ferran.

In: Phycologia, Vol. 42, No. 4, 07.2003, p. 384-392.

Research output: Contribution to journalArticle

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