Feeding of [5,5-2H(2)]-1-desoxy-D-xylulose and [4,4,6,6,6-2H(5)]-mevalolactone to a geosmin-producing Streptomyces sp. and Fossombronia pusilla.
The biosynthesis of the trisnor sesquiterpenoid geosmin (4,8a-dimethyl-octahydro-naphthalen-4a-ol) (1) was investigated by feeding labeled [5,5-2H(2)]-1-desoxy-D-xylulose (11), [4,4,6,6,6-(2)H(5)]-mevalolactone (7) and [2,2-2H(2)]-mevalolactone (9) to Streptomyces sp. JP95 and the liverwort Fossombronia pusilla. The micro-organism produced geosmin via the 1-desoxy-D-xylulose pathway, whereas the liverwort exclusively utilized mevalolactone for terpenoid biosynthesis. Analysis of the labeling pattern in the resulting isotopomers of geosmin (1) by mass spectroscopy (EI/MS) revealed that geosmin is synthesized in both organisms by cyclization of farnesyl diphosphate to a germacradiene-type intermediate 4. Further transformations en route to geosmin (1) involve an oxidative dealkylation of an i-propyl substituent, 1,2-reduction of a resulting conjugated diene, and bicyclization of a germacatriene intermediate 13. The transformations largely resemble the biosynthesis of dehydrogeosmin (2) in cactus flowers but differ with respect to the regioselectivity of the side chain dealkylation and 1,2-reduction
Spiteller
Dieter
D
Max-Planck-Institut für Chemische Okologie, Winzerlaer Strasse 10, Jena, Germany.
Jux
Andreas
A
Piel
Jörn
J
Boland
Wilhelm
W
D000478:Alkylation; D003500:Cyclization; D003903:Deuterium; D035926:Hepatophyta / Q000145:classification / Q000378:metabolism*; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D009284:Naphthols / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D011106:Polyisoprenyl Phosphates / Q000737:chemistry / Q000378:metabolism; D012717:Sesquiterpenes; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D013302:Streptomyces / Q000378:metabolism*; D014996:Xylulose / Q000737:chemistry / Q000378:metabolism*
C472750:(4,4,6,6,6-2H(5))-mevalolactone; D007783:Lactones; D009284:Naphthols; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; D014996:Xylulose; C004808:farnesyl pyrophosphate; D003903:Deuterium; C001278:geosmin