A Monooxygenase from Boreostereum vibrans Catalyzes Oxidative Decarboxylation in a Divergent Vibralactone Biosynthesis Pathway

Article abstract of DOI:10.1002/anie.201510928

The oxidative decarboxylation of prenyl 4-hydroxybenzoate to prenylhydroquinone has been frequently proposed for the biosynthesis of prenylated (hydro)quinone derivates (sometimes meroterpenoids), yet no corresponding genes or enzymes have so far been reported. A FAD-binding monooxygenase (VibMO1) was identified that converts prenyl 4-hydroxybenzoate into prenylhydroquinone and is likely involved in the biosynthesis of vibralactones and other meroterpenoids in the basidiomycete Boreostereum vibrans. Feeding of 3-allyl-4-hydroxybenzylalcohol, an analogue of the vibralactone pathway intermediate 3-prenyl-4-hydroxybenzylalcohol, generated 20 analogues with different scaffolds. This demonstrated divergent pathways to skeletally distinct compounds initiating from a single precursor, thus providing the first insight into a novel biosynthetic pathway for 3-substituted γ-butyrolactones from a shikimate origin.

Full text of DOI:10.1002/anie.201510928

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201510928
German Edition: DOI: 10.1002/ange.201510928
Biosynthesis
A Monooxygenase from Boreostereum vibrans Catalyzes Oxidative
Decarboxylation in a Divergent Vibralactone Biosynthesis Pathway
Yan-Long Yang, Hui Zhou, Gang Du, Ke-Na Feng, Tao Feng, Xiao-Li Fu, Ji-Kai Liu,* and
Ying Zeng*
Abstract: The oxidative decarboxylation of prenyl 4-hydroxy-
benzoate to prenylhydroquinone has been frequently proposed
for the biosynthesis of prenylated (hydro)quinone derivates
(sometimes meroterpenoids), yet no corresponding genes or
enzymes have so far been reported. A FAD-binding mono-
oxygenase (VibMO1) was identified that converts prenyl 4-
hydroxybenzoate into prenylhydroquinone and is likely
involved in the biosynthesis of vibralactones and other
meroterpenoids in the basidiomycete Boreostereum vibrans.
Feeding of 3-allyl-4-hydroxybenzylalcohol, an analogue of the
vibralactone pathway intermediate 3-prenyl-4-hydroxybenzy-
lalcohol, generated 20 analogues with different scaffolds. This
demonstrated divergent pathways to skeletally distinct com-
pounds initiating from a single precursor, thus providing the
first insight into a novel biosynthetic pathway for 3-substituted
g-butyrolactones from a shikimate origin.
bers of scaffold variations.[5] Further insight into how struc-
tural diversity is expanded from relatively few fundamental
blocks is therefore necessary to promote the development of
creative approaches for the skeletal diversification of com-
pounds. With this aim in mind, our attention was captured by
the basidiomycete fungus Boreostereum vibrans (syn. Stereum
vibrans), since more than thirty metabolites with eight distinct
scaffolds (see Section S1 in the Supporting Information) were
identified in our ongoing chemistry research on B. vibrans.
These compounds share common C5 prenyl marks, thus
suggesting that they may also share an early intermediate.
Based on our recent elucidation of the biosynthetic pathway
for vibralactone (10),[6] we speculate that 3-prenyl-4-hy-
droxybenzylalcohol (1) may lead to different vibralactones
via a divergent biosynthetic pathway, and an enzyme catalyz-
ing oxidative decarboxylation of 3-prenyl 4-hydroxybenzoate
(3) to prenylhydroquinone (4) can be expected (Figure 1).
Conversions similar to 3!4 have been proposed to occur in
the biosynthesis of shikonin[7] from the medicinal plant
Lithospermum erythrorhizon and meroterpenoids from the
basidiomycete fungi,[8] yet no corresponding genes or
enzymes have so far been reported. Still unknown are the
enzymes responsible for the successive decarboxylation and
hydroxylation of 5-methoxy-4-hydroxy-3-hexaprenyl ben-
zoate, an intermediate in yeast coenzyme Q biosynthesis.[9]
Given that the enzyme for this conversion has been over-
looked, and since only a few of the biosynthetic genes and
enzymes in basidiomycetes have been functionally character-
ized,[10] we set out to identify the relevant enzyme first.
We began with MNX1, a fungal NAD(P)H-dependent
flavoenzyme identified in the pathogenic yeast Candida
parapsilosis to specifically convert 4-hydroxybenzoate (4-
HBA) into 1,4-dihydroxybenzene (hydroquinone) and prob-
ably involved in lignin degradation.[11] By using MNX1 as
a probe, a homologue with 42% identity, designated VibMO1,
was found in our B. vibrans genome draft assembly to encode
a putative FAD-binding monooxygenase and aromatic-ring
hydroxylase (see Section S2.1 in the Supporting Information).
Furthermore, the formation of 4a (an analogue of 4) from 3a
(an analogue of 3) was evident in the fungal cell-free system
(see Section S2.2), thus indicating that the relevant enzyme is
rather active. In an attempt to identify VibMO1, gene
constructs were subcloned into a pET expression vector to
achieve higher expression levels in E. coli. When the E. coli
cell lysate as crude recombinant enzyme was incubated with 3,
3a, or 4-HBA, the production of 4, 4a, or hydroquinone was
observed, respectively. The purified recombinant VibMO1
was further confirmed to be active for the above substrates;
the heat-denatured enzyme control yielded no detectable
N
atural products with architecturally distinct scaffolds
remain attractive for the discovery of potential drugs and
biological probes.[1] To collect new compounds with privileged
skeletons, however, is becoming more challenging. Through
various combinations of chemical and biosynthetic
approaches,[2] large numbers of structurally interesting and
biologically active natural product analogues have been
generated to focus on a common scaffold in each case.[3] On
the other side, biosynthetic machineries usually accommodate
divergent pathways to produce a dazzling array of architec-
turally distinct skeletons from only a handful of basic building
blocks. For example, terpenoids, which comprise the largest
group of natural products, can ultimately be made up from
a C5 isoprene unit. Terpene biosynthesis thus provides
a prominent example of natureꢀs strategy for combinatorial
synthesis and diversity.[4] This strategy has inspired the
chemical synthesis of compounds with unprecedented num-
[*] Y.-L. Yang, H. Zhou, G. Du, K.-N. Feng, Dr. T. Feng, X.-L. Fu,
Prof. Dr. J.-K. Liu, Prof. Y. Zeng
State Key Laboratory of Phytochemistry and Plant Resources in West
China, Kunming Institute of Botany, Chinese Academy of Sciences
Kunming 650201, Yunnan (China)
E-mail: jkliu@mail.kib.ac.cn
biochem@mail.kib.ac.cn
Homepage: http://groups.english.kib.cas.cn/Phytochem/zy/
Y.-L. Yang, H. Zhou, G. Du, K.-N. Feng
University of Chinese Academy of Sciences, Beijing 100049 (China)
Dr. T. Feng, Prof. Dr. J.-K. Liu
School of Pharmaceutical Sciences
South-Central University for Nationalities, Wuhan 430074 (China)
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201510928.
Angew. Chem. Int. Ed. 2016, 55, 5463 –5466
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5463

Angewandte
Communications
Chemie
Figure 1. Proposed divergent pathways for vibralactones and other meroterpenoids in normal and 1a feeding broths of B. vibrans. R=allyl for
analogues with compound designations containing a; R=prenyl for natural products. All numbered compounds were purified from the cultures,
apart from 1–4 and 1a, which were synthesized and thoroughly characterized by NMR (see Section S4).
products (Figure 2A and Section S2.3). VibMO1 did not show
activity with salicylate, which is in agreement with its low
similarity (21%) to shyA, a verified salicylate hydroxylase
from the ascomycete fungus Epichlo festucae.[12] We next
screened for sequences similar to VibMO1 in the published
genomes of fungi known to produce prenylated quinones and
hydroquinones. As shown in the phylogenetic tree (Fig-
ure 2B, see Section S2.1), VibMO1 clustered with putative
enzymes of those producers and closely related to MNX1. In
contrast, VibMO1 is quite distant from Coq6 and shyA, which
indicates stringent substrate specificity, hence leading to
distinct enzymatic pathways. Based on RNA-seq analyses, the
VibMO1 transcripts significantly accumulated in the mycelia
on days 14 and 20. Interestingly, the B. vibrans native
metabolites 4 and 8 were obviously present on days 16 and
22, as evidenced from a time-course metabolite LC/MS
profiling (see Section S3).The oxidative cyclization of 4 to 5 is
common, and 4 would give 8 through a unique pathway
(Figure 1). Oxidative decarboxylation by the enzyme
VibMO1 can afford 4 from 3, which is structurally similar to
1. LC/MS analyses of the fungal native metabolites confirmed
the presence of 1, the aryl ring of which is known to originate
from a shikimate pathway.[6b] VibMO1, catalyzing the oxida-
tive decarboxylation of 3-prenyl 4-hydroxybenzoate (3) to
prenylhydroquinone (4), can thus be considered as the
enzyme most likely to be involved in the biosynthesis of
Figure 2. A) LC/MS analysis of the VibMO1 activity by single-ion monitoring of [MÀH]À at m/z=177 for the enzymatic product 4. B) Phylogenetic
connection of VibMO1 (GenBank: KU668560) and its fungal homologues. The tree scale was modified to accommodate the chemical structures
(see Section S2). Shown at the top of the tree are the corresponding prenyl(hydro)quinone derivates or the verified enzymatic reactions of each
fungus.
5464 www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 5463 –5466

Angewandte
Communications
Chemie
vibralactones (8) and other meroterpenoids (5) in B. vibrans
pathway.[21] Analogues 11a and 11a1 were obtained from 1a in
fungus (see Section S1). Our research gives rise to a shikimate
origin for the nonterpenoid moieties, despite the fact that
most prenylated quinones and hydroquinones are confirmed
to have mixed polyketide/terpenoid origin.[13] The VibMO1
catalysis mechanism could potentially resemble the oxidative
hydroxylation/decarboxylation of 4-HBA by MNX1 in C.
parapsilosis yeast.[11b]
this study, which strongly suggests a shikimate origin for the
featured moieties of these metabolites in B. vibrans. The
pathway to 11 (Figure 1) may share a process with that of
veratryl alcohol cleavage during lignin degradation in the
Phanerochaete chrysosporium fungus.[22] Similar transforma-
tions have been proposed to occur in the synthesis of the
fungal polyketides biosynthesis of patulin[23] and aculins.[15]
Finally, by analogy, we propose the pathway for 13 to initiate
with C2 extension of 2a by a pyruvate decarboxylase, followed
by reduction (Figure 1). Similar pathways have been identi-
fied in basidiomycetes for the biosynthesis of chloroarylpro-
pane diols and fomannoxin derivates.[24] Although our
collection lacked analogues of 14–17, signals corresponding
to the putative ions were detected in the 1a feeding broth (see
Section S3.2). In addition, the dimeric analogues 20a–23a
were evaluated for inhibition of platelet aggregation (see
Section S5).
This study affords in vivo and in vitro verification of the
oxidative decarboxylation of 4-hydroxybenzoates. This led to
the discovery and first genetic and biochemical character-
ization of a FAD-binding monooxygenase (VibMO1) that
converts prenyl 4-hydroxybenzoate into prenylhydroquinone
and is likely involved in the biosynthesis of vibralactones and
other meroterpenoids in B. vibrans. This identification of
VibMO1 will also be informative for the determination of
enzymes essential for similar conversion steps in the biosyn-
thesis of yeast coenzyme Q and plant prenyl(hydro)quinone
derivates, where the oxidative decarboxylation of (poly)-
prenyl hydroxybenzoates to their hydroquinones is under-
stood to occur yet no corresponding genes or enzymes have so
far been described. This study also demonstrates divergent
biosynthetic pathways toward distinct scaffolds from a single
precursor. To create skeletal diversification of compounds,
further insight into natureꢀs strategy for expanding structural
diversity is needed.
Next, we investigated whether 1 can form different
vibralactones through divergent pathways, based on the
traditional platform of precursor-directed biosynthesis.[3a,c,e, 14]
Since an allyl C3 mark is extremely rare in natural products
from higher fungi, compound 1a, an analogue of 1 that
contains an allyl rather than a prenyl moiety, was synthesized
and fed (2 mm) to a culture (500 mL) of B. vibrans on day 12
after inoculation. The culture broth was harvested after an
additional ten days of incubation to provide crude extracts for
LC/MS analyses. While vibralactones 9 and 10 were abundant
in both normal and feeding broths, signals corresponding to
the quasimolecular ions [M+Na]+ at m/z 203 for putative
analogues 9a and 10a were exclusively revealed in the 1a
feeding broth (see Section S3.2 in the Supporting Informa-
tion). Scale-up feedings and systematic purification afforded
a collection of thirteen new compounds and seven compounds
known solely from synthetic chemistry, all arising from 1a.
Their structures were elucidated on the basis of extensive
spectroscopic analysis (ESI-MS, HR-ESI-MS, and 1D and 2D
NMR) and by comparison of their NMR data with those
reported in the literature (see Section S1,S4).
Furthermore, divergent pathways in B. vibrans were
clarified through evidence of analogous intermediates. As
shown in Figure 1, the production of 2a–6a in the feedings
reveals reliable oxidative decarboxylation of 3a to 4a by
VibMO1 in vivo, and suggests a reasonable route of 1a!
2a!3a!4a!6a. Likewise, the conversion of 3 into 4 is
required for 1 to give 5 and 8. The next three steps from 4
toward 8 may be closely analogous to those proposed for
lignin degradation in yeast[11c] and aculins biosynthesis in
Aspergillus aculeatus.[15] It is reasonable that subsequent
decarboxylation to 7a, the lactonization of which would
eventually form an analogue of 8, takes place. 3-substituted g-
butyrolactones such as 8 found in natural products display
various biological activities,[16] which has prompted a number
of research efforts towards their chemical synthesis.[17]
Compared to its streptomycete congeners, blastmycinone
and butenolide, which are formed through the polyketide/
peptide hybrid antimycin biosynthetic pathway,[3f, 18] the 3-
substituted g-butyrolactone 8 is distinct in starting from an
aryl ring of shikimate origin. The pathway to 8 with key
intermediacy from analogues 4a and 7a is unusual and the
first time such a pathway has been described in natural
product chemistry.
Acknowledgements
This work was supported by the grants from the National
Natural Science Foundation of China (21572237,
81561148013). We thank Dr. Jing Yang from the Instrument
Center (Kunming Institute of Botany) for determination of
the absolute configuration of compound 11a. We are also very
grateful to the anonymous reviewers for their helpful com-
ments.
Keywords: biosynthesis · decarboxylation · enzymes ·
meroterpenoid · natural products
How to cite: Angew. Chem. Int. Ed. 2016, 55, 5463–5466
Angew. Chem. 2016, 128, 5553–5556
The vibralactone (10) pathway starting from 1 was further
verified by the formation of 9a and 10a, since 1a is
transformed along the native pathway by analogous reactions
to those for 1. Vibralactone J (11) and its analogues are 4-
substituted 2(5H)-furanones, which are of interest both in
natural product chemistry[19] and synthetic chemistry.[20] Most
of them are believed to originate from a terpene biosynthesis
[1] a) D. J. Newman, G. M. Cragg, J. Nat. Prod. 2012, 75, 311 – 335;
b) G. M. Cragg, D. J. Newman, Biochim. Biophys. Acta Gen.
Subj. 2013, 1830, 3670 – 3695.
[2] a) A. Kirschning, F. Hahn, Angew. Chem. Int. Ed. 2012, 51,
4012 – 4022; Angew. Chem. 2012, 124, 4086 – 4096; b) R. J. Goss,
S. Shankar, A. A. Fayad, Nat. Prod. Rep. 2012, 29, 870 – 889.
Angew. Chem. Int. Ed. 2016, 55, 5463 –5466
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5465

Angewandte
Communications
Chemie
[3] a) E. McCoy, S. E. OꢀConnor, J. Am. Chem. Soc. 2006, 128,
14276 – 14277; b) A. S. Eustµquio, B. S. Moore, Angew. Chem.
Int. Ed. 2008, 47, 3936 – 3938; Angew. Chem. 2008, 120, 4000 –
4002; c) S. Grüschow, E. J. Rackham, B. Elkins, P. L. Newill,
L. M. Hill, R. J. Goss, ChemBioChem 2009, 10, 355 – 360; d) W.
Runguphan, J. J. Maresh, S. E. OꢀConnor, Proc. Natl. Acad. Sci.
USA 2009, 106, 13673 – 13678; e) B. R. Clark, S. OꢀConnor, D.
Fox, J. Leroy, C. D. Murphy, Org. Biomol. Chem. 2011, 9, 6306 –
6311; f) Y. Yan, J. Chen, L. Zhang, Q. Zheng, Y. Han, H. Zhang,
D. Zhang, T. Awakawa, I. Abe, W. Liu, Angew. Chem. Int. Ed.
2013, 52, 12308 – 12312; Angew. Chem. 2013, 125, 12534 – 12538;
g) W. Runguphan, S. E. OꢀConnor, Org. Lett. 2013, 15, 2850 –
2853; h) Y. Tian, N. Jiang, A. H. Zhang, C. J. Chen, X. Z. Deng,
W. J. Zhang, R. X. Tan, Org. Lett. 2015, 17, 1457 – 1460.
[4] a) J. Buckingham, Dictionary of Natural Products (on-line web
edition), Chapman & Hall/CRC Press, 2002; b) D. W. Christian-
son, Chem. Rev. 2006, 106, 3412 – 3442.
[5] a) H. Mizoguchi, H. Oikawa, H. Oguri, Nat. Chem. 2014, 6, 57 –
64; b) T. Asai, K. Tsukada, S. Ise, N. Shirata, M. Hashimoto, I.
Fujii, K. Gomi, K. Nakagawara, E. N. Kodama, Y. Oshima, Nat.
Chem. 2015, 7, 737 – 743.
[6] a) D.-Z. Liu, F. Wang, T.-G. Liao, J.-G. Tang, W. Steglich, H.-J.
Zhu, J.-K. Liu, Org. Lett. 2006, 8, 5749 – 5752; b) P.-J. Zhao, Y.-L.
Yang, L. Du, J.-K. Liu, Y. Zeng, Angew. Chem. Int. Ed. 2013, 52,
2298 – 2302; Angew. Chem. 2013, 125, 2354 – 2358.
Holesova, M. Jakubkova, I. Zavadiakova, I. Zeman, L. Tomaska,
J. Nosek, Microbiology 2011, 157, 2152 – 2163.
[12] K. V. Ambrose, Z. Tian, Y. Wang, J. Smith, G. Zylstra, B. Huang,
F. C. Belanger, Sci. Rep. 2015, 5, 10939.
[13] a) S. N. Sunassee, M. T. Davies-Coleman, Nat. Prod. Rep. 2012,
29, 513 – 535; b) Y. Matsuda, I. Abe, Nat. Prod. Rep. 2016, 33,
26 – 53.
[14] a) Y. Ye, K. Aulinger, N. Arnold, W. Spahl, W. Steglich,
Tetrahedron Lett. 1997, 38, 8013 – 8016; b) P. Spiteller, M.
Rüth, F. von Nussbaum, W. Steglich, Angew. Chem. Int. Ed.
2000, 39, 2754 – 2756; Angew. Chem. 2000, 112, 2864 – 2866; c) S.
Peters, P. Spiteller, J. Nat. Prod. 2006, 69, 1809 – 1812.
[15] L. M. Petersen, D. K. Holm, C. H. Gotfredsen, U. H. Mortensen,
T. O. Larsen, ChemBioChem 2015, 16, 2200 – 2204.
[16] a) K. W. Cho, H.-S. Lee, J.-R. Rho, T. S. Kim, S. J. Mo, J. Shin, J.
ˇ
Nat. Prod. 2001, 64, 664 – 667; b) T. Rezanka, K. Sigler, Eur. J.
Org. Chem. 2006, 4277 – 4284; c) N. Agrawal, D. Pareek, S.
Dobhal, M. C. Sharma, Y. C. Joshi, M. P. Dobhal, Chem.
Biodiversity 2013, 10, 394 – 400.
[17] a) R. S. Ferrarini, A. A. Dos Santos, J. V. Comasseto, Tetrahe-
dron 2012, 68, 10601 – 10610; b) S. I. Lee, J. H. Jang, G.-S.
Hwang, D. H. Ryu, J. Org. Chem. 2013, 78, 770 – 775; c) S. J.
Gharpure, L. N. Nanda, M. K. Shukla, Org. Lett. 2014, 16, 6424 –
6427.
[18] R. Riclea, B. Aigle, P. Leblond, I. Schoenian, D. Spiteller, J. S.
Dickschat, ChemBioChem 2012, 13, 1635 – 1644.
[7] a) K. Yazaki, H. Matsuoka, T. Ujihara, F. Sato, Plant Biotechnol.
1999, 16, 335 – 342; b) K. Yazaki, M. Kunihisa, T. Fujisaki, F.
Sato, J. Biol. Chem. 2002, 277, 6240 – 6246.
[8] a) A. Mühlbauer, J. Beyer, W. Steglich, Tetrahedron Lett. 1998,
39, 5167 – 5170; b) M. Lang, A. Mühlbauer, C. Gräf, J. Beyer, S.
Lang-Fugmann, K. Polborn, W. Steglich, Eur. J. Org. Chem.
2008, 816 – 825; c) M. Lang, A. Mühlbauer, E. Jägers, W.
Steglich, Eur. J. Org. Chem. 2008, 3544 – 3551; d) Q. Luo, L.
Tian, L. Di, Y.-M. Yan, X.-Y. Wei, X.-F. Wang, Y.-X. Cheng, Org.
Lett. 2015, 17, 1565 – 1568.
[19] a) Y. Wang, J. B. Gloer, J. A. Scott, D. Malloch, J. Nat. Prod.
1993, 56, 341 – 344; b) S. L. Midland, N. T. Keen, J. J. Sims, J. Org.
Chem. 1995, 60, 1118 – 1119; c) S. P. Gunasekera, P. J. McCarthy,
M. Kelly-Borges, E. Lobkovsky, J. Clardy, J. Am. Chem. Soc.
1996, 118, 8759 – 8760.
[20] a) M.-L. Yao, M.-Z. Deng, J. Org. Chem. 2000, 65, 5034 – 5036;
b) J. Wu, Q. Zhu, L. Wang, R. Fathi, Z. Yang, J. Org. Chem. 2003,
68, 670 – 673; c) J. Boukouvalas, S. CôtØ, B. Ndzi, Tetrahedron
Lett. 2007, 48, 105 – 107.
[9] a) I. Gonzµlez-Mariscal, E. Garcia-Testón, S. Padilla, A. Martín-
Montalvo, T. Pomares-Viciana, L. Vazquez-Fonseca, P. Gan-
dolfo-Domínguez, C. Santos-OcaÇa, IUBMB Life 2014, 66, 63 –
70; b) M. Kawamukai, Biosci. Biotechnol. Biochem. 2015, 79, 1 –
11.
[10] a) G. T. Wawrzyn, M. B. Quin, S. Choudhary, F. López-Gallego,
C. Schmidt-Dannert, Chem. Biol. 2012, 19, 772 – 783; b) G.
Lackner, M. Bohnert, J. Wick, D. Hoffmeister, Chem. Biol. 2013,
20, 1101 – 1106; c) M. B. Quin, C. M. Flynn, G. T. Wawrzyn, S.
Choudhary, C. Schmidt-Dannert, ChemBioChem 2013, 14,
2480 – 2491; d) J. Braesel, S. Gçtze, F. Shah, D. Heine, J.
Tauber, C. Hertweck, A. Tunlid, P. Stallforth, D. Hoffmeister,
Chem. Biol. 2015, 22, 1325 – 1334.
[21] a) A. Carotenuto, E. Fattorusso, V. Lanzotti, S. Magno, R.
Carnuccio, F. DꢀAcquisto, Tetrahedron 1997, 53, 7305 – 7310;
b) H. Bousserouel, M. Litaudon, B. Morleo, M.-T. Martin, O.
Thoison, O. Nosjean, J. A. Boutin, P. Renard, T. SØvenet,
Tetrahedron 2005, 61, 845 – 851; c) U. Krings, D. Hapetta, R. G.
Berger, Appl. Microbiol. Biotechnol. 2008, 78, 533 – 541.
[22] R. ten Have, M. C. R. Franssen, FEBS Lett. 2001, 487, 313 – 317.
[23] M. P. Artigot, N. Loiseau, J. Laffitte, L. Mas-Reguieg, S. Tadrist,
I. P. Oswald, O. Puel, Microbiology 2009, 155, 1738 – 1747.
[24] a) P. J. Silk, J. B. Macaulay, FEMS Microbiol. Lett. 2003, 228, 11 –
19; b) D. Hansson, A. Menkis, A. Olson, J. Stenlid, A. Broberg,
M. Karlsson, Phytochemistry 2012, 84, 31 – 39.
[11] a) W. J. H. van Berkel, M. H. M. Eppink, W. J. Middelhoven, J.
Vervoort, I. M. C. M. Rietjens, FEMS Microbiol. Lett. 1994, 121,
207 – 215; b) M. H. M. Eppink, S. A. Boeren, J. Vervoort,
W. J. H. van Berkel, J. Bacteriol. 1997, 179, 6680 – 6687; c) Z.
Received: November 25, 2015
Revised: February 9, 2016
Published online: March 23, 2016
5466 www.angewandte.org
ꢀ 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 5463 –5466