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Biosynthesis of Marine Natural Products: Isolation and Characterization of a Myrcene Synthase from Cultured Tissues of the Marine Red Alga Ochtodes secundiramea

https://doi.org/10.1006/abbi.2002.2780Get rights and content

Abstract

The acyclic monoterpene myrcene is the likely progenitor of the unusual cytotoxic halogenated monoterpenes that are found in marine algae and that function as feeding deterrents to herbivores. Myrcene synthase was isolated from suspension cultures of the marine red alga Ochtodes secundiramea, representing the first enzyme of this type from a marine organism. The algal myrcene synthase produces exclusively myrcene from the natural substrate geranyl diphosphate (GDP), utilizes Mg+2 as the required divalent metal ion cofactor, has a molecular mass of about 69 kDa, and exhibits a pH optimum near 7.2. These features are similar to those of monoterpene synthases from terrestrial organisms. When incubated with neryl diphosphate (the cis-isomer of GDP), the O. secundiramea myrcene synthase produces the cyclic monoterpene limonene, whereas incubation with (±)linalyl diphosphate (the tertiary allylic isomer of geranyl diphosphate) yields both acyclic and cyclic monoterpenes. These results suggest that the enzyme is incapable of isomerizing geranyl diphosphate to linalyl diphosphate, a feature common to all monoterpene cyclases from terrestrial sources. The limited catalytic capability of the myrcene synthase may reflect the ancient evolutionary origin of the producing organism. The ability to assay this enzyme in cultured algae, grown under strictly defined conditions, provides an unparalleled opportunity to delineate factors eliciting the biosynthesis of this class of secondary metabolites, to investigate the metabolic pathway leading to the halogenated monoterpenes, and to determine their role in the chemical ecology of marine algae.

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  • Cited by (18)

    • Selective production of the acyclic monoterpene β-myrcene by microplantlet suspension cultures of the macrophytic marine red alga Ochtodes secundiramea under nutrient perfusion cultivation with bromide-free medium

      2018, Algal Research
      Citation Excerpt :

      All of these isoprenoid precursors require phosphate, which was continuously supplied to the culture suspension. In earlier studies, we showed that β-myrcene in O. secundiramea microplantlets was the exclusive product of unique algal myrcene synthase using GPP as the sole substrate [18,19]. Downstream halogenation of β-myrcene to halogenated monoterpenes is also presented at the bottom of Fig. 10.

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    Financial support for this project was provided in part through NIH Grant GM31354 (to R.B.C.). G. L. Rorrer gratefully acknowledges the National Science Foundation, Division of Bioengineering and Environmental Systems (BES-9810797), for supporting the development of the culture systems used in this study.

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    To whom correspondence and reprint requests should be addressed at current address: USDA, Cereal Crops Research Unit, 501 Walnut St. Madison, WI 53705. Fax: (608) 264-5528. E-mail: [email protected].

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