Retinal biosynthesis in Eubacteria: In vitro characterization of a novel carotenoid oxygenase from Synechocystis sp. PCC 6803

Sandra Ruch, Peter Beyer, Hansgeorg Ernst, Salim Al-Babili*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


Retinal and its derivatives represent essential compounds in many biological systems. In animals, they are synthesized through a symmetrical cleavage of β-carotene catalysed by a monooxygenase. Here, we demonstrate that the open reading frame sII1541 from the cyanobacterium Synechocystis sp. PCC 6803 encodes the first eubacterial, retinal synthesizing enzyme (Diox1) thus far reported. In contrast to enzymes from animals, Diox1 converts β-apo-carotenals instead of β-carotene into retinal in vitro. The identity of the enzymatic product was proven by HPLC, GC-MS and in a biological test. Investigations, of the stereospecifity showed that Diox1 cleaved only the all-trans form of β-apo-8′-carotenal, yielding all-tans-retinal. However, Diox1 exhibited wide substrate specificity with respect to chain-lengths and functional end-groups. Although with divergent Km and Vmax values, the enzyme converted β-apo-carotenals, (3R)-3-OH-β-apo-carotenals as well as apo-lycopenals into retinal, (3R)-3-hydroxy-retinal and acycloretinal respectively. In addition, the alcohols of these substrates were cleaved to yield the corresponding retinal derivatives.

Original languageEnglish (US)
Pages (from-to)1015-1024
Number of pages10
JournalMolecular Microbiology
Issue number4
StatePublished - Feb 1 2005

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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