Spearmint terpenoid biosynthesis

Proposed terpenoid essential oil biosynthetic pathway in native spearmint (Mentha spicata) (only major products shown)

Spearmint terpenoid biosynthesis pathway

Gene/enzyme annotation for terpenoid essential oil biosynthesis in spearmint:
  Annotation Comments Gene Protein
(1) Geranyl diphosphate synthase; Dimethylallyltranstransferase Not characterized from spearmint; For more information see peppermint    
(2) (2E,6E)-Farnesyl diphosphate synthase Not characterized from spearmint; For more information see peppermint    
(3) 1,8-Cineole synthase Not yet characterized    
(4) β-Pinene synthase Not characterized from spearmint; Although (-)-limonene synthase produces β-pinene as a side product, the amounts of this monoterpene in the oil are fairly high, so we hypothesize that spearmint expresses a dedicated β-pinene synthase    
(5) β-Caryophyllene synthase Not yet characterized    
(6) Germacrene D synthase Not yet characterized    
(7) (-)-(4S)-Limonene synthase Myrcene, α-pinene, β-pinene are side products of limonene synthase catalysis; Crystal structure available. MHC4SLSP EC 4.2.3.16
(8) (-)-4S-Limonene-6-hydroxylase; (S)-Limonene 6-monooxygenase   AF124815 EC 1.14.13.48
(9) (-)-Carveol dehydrogenase Almost identical to peppermint (-)-isopiperitenone reductase. Gene product has not been characterized functionally.    
(10) (-)-trans-Carveol reductase Not yet characterized    
(11) (-)-trans-Dihydrocarveol acetyltransferase Not yet characterized    
(12) (-)-cis-Carveol acetyltransferase Not yet characterized    
References (reviews):

Croteau et al. (2005) Naturwissenschaften 92, 562-577.
Lange et al. (2014), in press.

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