This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Antibiotic Biosynthesis|
Expected Taxonomic Range:
The antibiotic albaflavenone was first isolated from a Streptomyces species from the species group Streptomyces albidoflavus, cluster 1. This compound had an earthy, camphor-like odor and was described as an α,β-unsaturated sesquiterpene ketone with a zizaene skeleton. It showed antimicrobial activity against Bacillus subtilis [Gurtler94]. It biosynthetic pathway in Streptomyces coelicolor A3(2) has been determined [Zhao08, Lin06a]. This pathway is also likely to occur in Streptomyces avermitilis based on the existence of a transcriptionally coupled, two-gene cluster in Streptomyces avermitilis encoding enzymes having 76% amino acid sequence identity with those of Streptomyces coelicolor. In addition, epi-isozizaene synthase activity was demonstrated for the corresponding Streptomyces avermitilis gene product (in [Zhao08]).
About This Pathway
In this pathway (2E,6E)-farnesyl diphosphate is cyclized in a Mg2+-dependent reaction to form the novel sesquiterpene metabolite (+)-epi-isozizaene [Lin06a, Zhao08]. This is followed by a two-step allylic oxidation of (+)-epi-isozizaene to form the 5-keto derivative albaflavenone via an epimeric mixture of (5S)-albaflavenol and (5R)-albaflavenol intermediates. All four compounds were detected in extracts of Streptomyces coelicolor A3(2) by gas chromatography/mass spectrometry [Zhao08].
This two-step oxidation of an allylic methylene to a conjugated ketone by a single cytochrome P450 enzyme is less common than the three-step oxidation of methyl groups to carboxylic acids catalyzed by other single cytochrome P450 enzymes (in [Zhao08]).
Gurtler94: Gurtler H, Pedersen R, Anthoni U, Christophersen C, Nielsen PH, Wellington EM, Pedersen C, Bock K (1994). "Albaflavenone, a sesquiterpene ketone with a zizaene skeleton produced by a streptomycete with a new rope morphology." J Antibiot (Tokyo) 47(4);434-9. PMID: 8195043
Lin06a: Lin X, Hopson R, Cane DE (2006). "Genome mining in Streptomyces coelicolor: molecular cloning and characterization of a new sesquiterpene synthase." J Am Chem Soc 128(18);6022-3. PMID: 16669656
Zhao08: Zhao B, Lin X, Lei L, Lamb DC, Kelly SL, Waterman MR, Cane DE (2008). "Biosynthesis of the Sesquiterpene Antibiotic Albaflavenone in Streptomyces coelicolor A3(2)." J Biol Chem 283(13);8183-9. PMID: 18234666
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