REVIEW: A New Alternative Non-mevalonate Pathway for Isoprenoid Biosynthesis in Eubacteria and Plants

V. A. Paseshnichenko

Bakh Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, Moscow, 117071 Russia; fax: (095) 954-27-32

Received July 22, 1997; Revision received October 22, 1997

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Data concerning the discovery of an alternative non-mevalonate pathway for isoprenoid biosynthesis leading to isopentenyl diphosphate formation are reviewed. This pathway has been discovered in experiments with several eubacteria producing triterpenoids of the hopane series. ¹³C-labeled acetate, glucose, and triose phosphates were used as precursors. The ¹³C-labeling patterns in isoprenoids were studied by ¹³C-NMR spectrometry. In eubacteria the universal C₅ precursor--isopentenyl diphosphate--did not appear to form via the classical acetate/mevalonate pathway, but via a novel glyceraldehyde 3-phosphate/pyruvate pathway. It is postulated that the condensation of the C₂ unit formed as a result of pyruvate decarboxylation with the C₃ unit (glyceraldehyde 3-phosphate) and the next transposition leads to the formation of the branched C₅ precursor--isopentenyl diphosphate. In Scenedesmus obliquus not only all plastid isoprenoids (carotenoids and prenyl side chains of chlorophylls and plastoquinone-9) were formed via this novel pathway, but also the non-plastid cytoplasmic sterols. In higher plants the plastid isoprenoids were formed via the glyceraldehyde 3-phosphate/pyruvate pathway, while the cytoplasmic sterols were formed via the acetate/mevalonate pathway.

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KEY WORDS: isoprenoids, carotenoids, triterpenoids of the hopane series, prenyl quinones, sterols, mevalonic acid, isopentenyl diphosphate, acetate, glucose, pyruvic acid, glyceraldehyde 3-phosphate, ¹³C-NMR

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