Occurrence of Cationic Intermediates and Deficient Control during the Enzymatic Cyclization of Squalene to Hopanoids

Pale-Grosdemange, Catherine; Feil, Corinna; Rohmer, Michel; Poralla, Karl

doi:10.1002/(sici)1521-3773(19980904)37:16<2237::aid-anie2237>3.3.co;2-0

Cited by 32 publications

(58 citation statements)

References 16 publications

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“…1B), if the fragment overlapped these loci upon alignment. Residues F601 and F605 are required to form the hopanoid cyclohexyl C and D rings respectively (Pale‐Gosdemange et al ., 1998; Merkofer et al ., 1999; Hoshino et al ., 2000). The presence of these motifs and other patterns (e.g.…”

Section: Discussionmentioning

confidence: 99%

Novel hopanoid cyclases from the environment

Pearson

Page

Jorgenson

et al. 2007

Environmental Microbiology

116

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Hopanoids are ubiquitous isoprenoid lipids found in modern biota, in recent sediments and in low-maturity sedimentary rocks. Because these lipids primarily are derived from bacteria, they are used as proxies to help decipher geobiological communities. To date, much of the information about sources of hopanoids has come from surveys of culture collections, an approach that does not address the vast fraction of prokaryotic communities that remains uncharacterized. Here we investigated the phylogeny of hopanoid producers using culture-independent methods. We obtained 79 new sequences of squalene-hopene cyclase genes (sqhC) from marine and lacustrine bacterioplankton and analysed them along with all 31 sqhC fragments available from existing metagenomics libraries. The environmental sqhCs average only 60% translated amino acid identity to their closest relatives in public databases. The data imply that the sources of these important geologic biomarkers remain largely unknown. In particular, genes affiliated with known cyanobacterial sequences were not detected in the contemporary environments analysed here, yet the geologic record contains abundant hopanoids apparently of cyanobacterial origin. The data also suggest that hopanoid biosynthesis is uncommon: < 10% of bacterial species may be capable of producing hopanoids. A better understanding of the contemporary distribution of hopanoid biosynthesis may reveal fundamental insight about the function of these compounds, the organisms in which they are found, and the environmental signals preserved in the sedimentary record.

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Section: Discussionmentioning

confidence: 99%

Novel hopanoid cyclases from the environment

Pearson

Page

Jorgenson

et al. 2007

Environmental Microbiology

116

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“…17 It has been shown that in a SHC-catalyzed reaction deprotonation takes place, in contrast to a LUP1 reaction, specifically from the (Z)-methyl group of the terminal isopropenyl moiety during hopene formation. 18 Water addition to the hopanyl cation is also stereospecific during hopanol formation, 18 although the stereochemistry of this water addition has not been established yet.…”

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confidence: 99%

Stereochemical Course in Water Addition during LUP1-Catalyzed Triterpene Cyclization

et al. 2006

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Arabidopsis thaliana LUP1 (At1g78970) catalyzes the cyclization of oxidosqualene into lupeol and 3beta,20-dihydroxylupane (lupanediol). The stereochemical course of water addition to the lupanyl cation was studied. The X-ray crystal structure of lupanylepoxide 3,5-dinitrobenzoate established the configuration of epoxide as 20S. LiAlD4 reduction of the epoxide enabled the chemical shift assignment of prochiral methyl groups at C20 of lupanediol. Correlation of these methyl groups with biosynthetic lupanediol from [1,2-(13)C(2)] acetate established the stereochemical course of water addition. [reaction: see text].

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“…The termination reaction was presumably presented by a polar amino acid (Glu45) associated with a water molecule for effectively abstracting the proton or hydroxylation of the cationic intermediate 65–67. In parallel, several putative cation‐stabilizing residues have been subjected to mutational studies to evaluate their importance in different stages of the squalene cyclization process 4,36,65,66,68–75. Different truncated cyclization products, ranging from monocyclic to pentacyclic triterpenoids, have been obtained from point mutations of Trp169, Ile261, Gln262, Pro263, Trp312, Phe365, Asp377, Tyr420, Trp489, Gly600, Phe601, Phe605, Leu607, Tyr609, and Tyr612.…”

Section: Models For Cyclase Evolution and Biological Studies Of Oxidomentioning

confidence: 99%

Saccharomyces cerevisiae oxidosqualene‐lanosterol cyclase: A chemistry–biology interdisciplinary study of the protein's structure–function–reaction mechanism relationships

Chang

Liu

et al. 2008

The Chemical Record

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The oxidosqualene cyclases (EC 5.4.99-) constitute a family of enzymes that catalyze diverse cyclization/rearrangement reactions of (3S)-2,3-oxidosqualene into a distinct array of sterols and triterpenes. The relationship between the cyclization mechanism and the enzymatic structure is extremely complex and compelling. This review covers the historical achievements of biomimetic studies and current progress in structural biology, molecular genetics, and bioinformatics studies to elucidate the mechanistic and structure-function relationships of the Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase-catalyzed cyclization/rearrangement reaction.

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Occurrence of Cationic Intermediates and Deficient Control during the Enzymatic Cyclization of Squalene to Hopanoids

Cited by 32 publications

References 16 publications

Novel hopanoid cyclases from the environment

Novel hopanoid cyclases from the environment

Stereochemical Course in Water Addition during LUP1-Catalyzed Triterpene Cyclization

Saccharomyces cerevisiae oxidosqualene‐lanosterol cyclase: A chemistry–biology interdisciplinary study of the protein's structure–function–reaction mechanism relationships

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