Different reaction mechanisms for cis- and trans-prenyltransferases

The catalytic and structural basis of archaeal glycerophospholipid biosynthesis

Archaeal glycerophospholipids are the main constituents of the cytoplasmic membrane in the archaeal domain of life and fundamentally differ in chemical composition compared to bacterial phospholipids. They consist of isoprenyl chains ether-bonded to glycerol-1-phosphate. In contrast, bacterial glycerophospholipids are composed of fatty acyl chains ester-bonded to glycerol-3-phosphate. This largely domain-distinguishing feature has been termed the “lipid-divide”. The chemical composition of archaeal membranes contributes to the ability of archaea to survive and thrive in extreme environments. However, ether-bonded glycerophospholipids are not only limited to extremophiles and found also in mesophilic archaea. Resolving the structural basis of glycerophospholipid biosynthesis is a key objective to provide insights in the early evolution of membrane formation and to deepen our understanding of the molecular basis of extremophilicity. Many of the glycerophospholipid enzymes are either integral membrane proteins or membrane-associated, and hence are intrinsically difficult to study structurally. However, in recent years, the crystal structures of several key enzymes have been solved, while unresolved enzymatic steps in the archaeal glycerophospholipid biosynthetic pathway have been clarified providing further insights in the lipid-divide and the evolution of early life.

A Slippery Scaffold: Synthesis and Recycling of the Bacterial Cell Wall Carrier Lipid

The biosynthesis of bacterial cell envelope polysaccharides such as peptidoglycan relies on the use of a dedicated carrier lipid both for the assembly of precursors at the cytoplasmic face of the plasma membrane and for the translocation of lipid linked oligosaccharides across the plasma membrane into the periplasmic space. This dedicated carrier lipid, undecaprenyl phosphate, results from the dephosphorylation of undecaprenyl pyrophosphate, which is generated de novo in the cytoplasm by undecaprenyl pyrophosphate synthase and released as a by-product when newly synthesized glycans are incorporated into the existing cell envelope. The de novo synthesis of undecaprenyl pyrophosphate has been thoroughly characterized from a structural and mechanistic standpoint; however, its dephosphorylation to the active carrier lipid form, both in the course of de novo synthesis and recycling, has only been begun to be studied in depth in recent years. This review provides an overview of bacterial carrier lipid synthesis and presents the current state of knowledge regarding bacterial carrier lipid recycling.

Peptidoglycan pathways: there are still more!

The discovery of 3rd and 4th generations of currently existing classes of antibiotics has not hindered bacterial resistance, which is escalating at an alarming global level. This review follows WHO recommendations through implementing new criteria for newly discovered antibiotics. These recommendations focus on abandoning old scaffolds and hitting new targets. In light of these recommendations, this review discusses seven bacterial proteins that no commercial antibiotics have targeted yet, alongside their reported chemical scaffolds.

Molecular Studies of the Protein Complexes Involving Cis-Prenyltransferase in Guayule (Parthenium argentatum), an Alternative Rubber-Producing Plant

Guayule (Parthenium argentatum) is a perennial shrub in the Asteraceae family and synthesizes a high quality, hypoallergenic cis-1,4-polyisoprene (or natural rubber; NR). Despite its potential to be an alternative NR supplier, the enzymes for cis-polyisoprene biosynthesis have not been comprehensively studied in guayule. Recently, implications of the protein complex involving cis-prenyltransferases (CPTs) and CPT-Binding Proteins (CBPs) in NR biosynthesis were shown in lettuce and dandelion, but such protein complexes have yet to be examined in guayule. Here, we identified four guayule genes - three PaCPTs (PaCPT1-3) and one PaCBP, whose protein products organize PaCPT/PaCBP complexes. Co-expression of both PaCBP and each of the PaCPTs could complemented the dolichol (a short cis-polyisoprene)-deficient yeast, whereas the individual expressions could not. Microsomes from the PaCPT/PaCBP-expressing yeast efficiently incorporated 14C-isopentenyl diphosphate into dehydrodolichyl diphosphates; however, NR with high molecular weight could not be synthesized in in vitro assays. Furthermore, co-immunoprecipitation and split-ubiquitin yeast 2-hybrid assays using PaCPTs and PaCBP confirmed the formation of protein complexes. Of the three PaCPTs, guayule transcriptomics analysis indicated that the PaCPT3 is predominantly expressed in stem and induced by cold-stress, suggesting its involvement in NR biosynthesis. The comprehensive analyses of these PaCPTs and PaCBP here provide the foundational knowledge to generate a high NR-yielding guayule.

Catalytic Role of Conserved Asparagine, Glutamine, Serine, and Tyrosine Residues in Isoprenoid Biosynthesis Enzymes

We report the results of an investigation into the catalytic role of highly conserved amide (asparagine, glutamine) and OH-containing (serine, tyrosine) residues in several prenyltransferases. We first obtained the X-ray structure of cyclolavandulyl diphosphate synthase containing two molecules of the substrate analog dimethylallyl (S)-thiolodiphosphate (DMASPP). The two molecules have similar diphosphate group orientations to those seen in other ζ-fold (cis- head-to-tail and head-to-middle) prenyltransferases with one diphosphate moiety forming a bidentate chelate with Mg²⁺ in the so-called S1 site (which is typically the allylic binding site in ζ-fold proteins) while the second diphosphate binds to Mg²⁺ in the so-called S2 site (which is typically the homoallylic binding site in ζ-fold proteins) via a single P1O1 oxygen. The latter interaction can facilitate direct phosphate-mediated proton abstraction via P1O2, or more likely by an indirect mechanism in which P1O2 stabilizes a basic asparagine species that removes H⁺, which is then eliminated via an Asn-Ser shuttle. The universal occurrence of Asn-Ser pairs in ζ-fold proteins leads to the idea that the highly conserved amide (Asn, Gln) and OH-containing (Tyr) residues seen in many "head-to-head" prenyltransferases such as squalene and dehydrosqualene synthase might play similar roles, in H⁺ elimination. Structural, bioinformatics and mutagenesis investigations indeed indicate an important role of these residues in catalysis, with the results of density functional theory calculations showing that Asn bound to Mg²⁺ can act as a general (imine-like) base, while Gln, Tyr and H₂O form a proton channel that is adjacent to the conventional (Asp-rich) "active site". Taken together, our results lead to mechanisms of proton-elimination from carbocations in numerous prenyltransferases in which neutral species (Asn, Gln, Ser, Tyr, H₂O) act as proton shuttles, complementing the more familiar roles of acidic groups (in Asp and Glu) that bind to Mg²⁺, and basic groups (primarily Arg) that bind to diphosphates, in isoprenoid biosynthesis.

Utilization of an intermediate of the methylerythritol phosphate pathway, (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate, as the prenyl donor substrate for various prenyltransferases

(E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) is an intermediate of the methylerythritol phosphate pathway. Utilization of HMBPP by lycopene elongase from Corynebacterium glutamicum, which is a UbiA-family prenyltransferase responsible for C₅₀ carotenoid biosynthesis, was investigated using an Escherichia coli strain that contained the exogenous mevalonate pathway as well as the carotenoid biosynthetic pathway. Inhibition of the endogenous methylerythritol phosphate pathway resulted in loss of the production of C₅₀ carotenoid flavuxanthin, while C₄₀ lycopene formation was retained. Overexpression of E. coli ispH gene, which encodes HMBPP reductase, also decreased the production of flavuxanthin in E. coli cells. These results indicate the preference of lycopene elongase for HMBPP instead of the previously proposed substrate, dimethylallyl diphosphate. Furthermore, several (all-E)-prenyl diphosphate synthases, which are classified in a distinct family of prenyltransferase, were demonstrated to accept HMBPP, which implies that the compound is more widely used as a prenyl donor substrate than was previously expected.

Site-directed mutagenesis switching a dimethylallyl tryptophan synthase to a specific tyrosine C3-prenylating enzyme

The tryptophan prenyltransferases FgaPT2 and 7-DMATS (7-dimethylallyl tryptophan synthase) from Aspergillus fumigatus catalyze C(4)- and C(7)-prenylation of the indole ring, respectively. 7-DMATS was found to accept l-tyrosine as substrate as well and converted it to an O-prenylated derivative. An acceptance of l-tyrosine by FgaPT2 was also observed in this study. Interestingly, isolation and structure elucidation revealed the identification of a C(3)-prenylated l-tyrosine as enzyme product. Molecular modeling and site-directed mutagenesis led to creation of a mutant FgaPT2_K174F, which showed much higher specificity toward l-tyrosine than l-tryptophan. Its catalytic efficiency toward l-tyrosine was found to be 4.9-fold in comparison with that of non-mutated FgaPT2, whereas the activity toward l-tryptophan was less than 0.4% of that of the wild-type. To the best of our knowledge, this is the first report on an enzymatic C-prenylation of l-tyrosine as free amino acid and altering the substrate preference of a prenyltransferase by mutagenesis.

C7-prenylation of tryptophanyl and O-prenylation of tyrosyl residues in dipeptides by an Aspergillus terreus prenyltransferase

During our search for novel prenyltransferases, a putative gene ATEG_04218 from Aspergillus terreus raised our attention and was therefore amplified from strain DSM 1958 and expressed in Escherichia coli. Biochemical investigations with the purified recombinant protein and different aromatic substrates in the presence of dimethylallyl diphosphate revealed the acceptance of all the tested tryptophan-containing cyclic dipeptides. Structure elucidation of the main enzyme products by NMR and MS analyses confirmed the attachment of the prenyl moiety to C-7 of the indole ring, proving the identification of a cyclic dipeptide C7-prenyltransferase (CdpC7PT). For some substrates, reversely C3- or N1-prenylated derivatives were identified as minor products. In comparison to the known tryptophan-containing cyclic dipeptide C7-prenyltransferase CTrpPT from Aspergillus oryzae, CdpC7PT showed a much higher substrate flexibility. It also accepted cyclo-L-Tyr-L-Tyr as substrate and catalyzed an O-prenylation at the tyrosyl residue, providing the first example from the dimethylallyltryptophan synthase (DMATS) superfamily with an O-prenyltransferase activity towards dipeptides. Furthermore, products with both C7-prenyl at tryptophanyl and O-prenyl at tyrosyl residue were detected in the reaction mixture of cyclo-L-Trp-L-Tyr. Determination of the kinetic parameters proved that (S)-benzodiazepinedione consisting of a tryptophanyl and an anthranilyl moiety was accepted as the best substrate with a K M value of 204.1 μM and a turnover number of 0.125 s(-1). Cyclo-L-Tyr-L-Tyr was accepted with a K M value of 1,411.3 μM and a turnover number of 0.012 s(-1).

Deciphering the metabolism of undecaprenyl-phosphate: the bacterial cell-wall unit carrier at the membrane frontier

During the biogenesis of bacterial cell-wall polysaccharides, such as peptidoglycan, cytoplasmic synthesized precursors should be trafficked across the plasma membrane. This essential process requires a dedicated lipid, undecaprenyl-phosphate that is used as a glycan lipid carrier. The sugar is linked to the lipid carrier at the inner face of the membrane and is translocated toward the periplasm, where the glycan moiety is transferred to the growing polymer. Undecaprenyl-phosphate originates from the dephosphorylation of its precursor undecaprenyl-diphosphate, with itself generated by de novo synthesis or by recycling after the final glycan transfer. Undecaprenyl-diphosphate is de novo synthesized by the cytosolic cis-prenyltransferase undecaprenyl-diphosphate synthase, which has been structurally and mechanistically characterized in great detail highlighting the condensation process. In contrast, the next step toward the formation of the lipid carrier, the dephosphorylation step, which has been overlooked for many years, has only started revealing surprising features. In contrast to the previous step, two unrelated families of integral membrane proteins exhibit undecaprenyl-diphosphate phosphatase activity: BacA and members of the phosphatidic acid phosphatase type 2 super-family, raising the question of the significance of this multiplicity. Moreover, these enzymes establish an unexpected link between the synthesis of bacterial cell-wall polymers and other biological processes. In the present review, the current knowledge in the field of the bacterial lipid carrier, its mechanism of action, biogenesis, recycling, regulation, and future perspective works are presented.

Antibacterial drug leads targeting isoprenoid biosynthesis

With the rise in resistance to antibiotics such as methicillin, there is a need for new drugs. We report here the discovery and X-ray crystallographic structures of 10 chemically diverse compounds (benzoic, diketo, and phosphonic acids, as well as a bisamidine and a bisamine) that inhibit bacterial undecaprenyl diphosphate synthase, an essential enzyme involved in cell wall biosynthesis. The inhibitors bind to one or more of the four undecaprenyl diphosphate synthase inhibitor binding sites identified previously, with the most active leads binding to site 4, outside the catalytic center. The most potent leads are active against Staphylococcus aureus [minimal inhibitory concentration (MIC)(90) ∼0.25 µg/mL], and one potently synergizes with methicillin (fractional inhibitory concentration index = 0.25) and is protective in a mouse infection model. These results provide numerous leads for antibacterial development and open up the possibility of restoring sensitivity to drugs such as methicillin, using combination therapies.

Characterization of the AggR regulon in enteroaggregative Escherichia coli

AggR is a transcriptional regulator of enteroaggregative Escherichia coli (EAEC) and has been proposed as the defining factor for typical EAEC strains. Expression of multiple putative virulence factors, including the aggregative adherence fimbriae (AAF), dispersin, the dispersin translocator Aat, and the Aai type VI secretion system, have been found to be regulated by AggR. Here, we confirm the existence of at least 44 AggR-regulated genes using DNA microarray and real-time quantitative reverse transcription-PCR (qRT-PCR); these genes include chromosomal and plasmid-borne loci and 19 previously unsuspected genes. Two previously uncharacterized virulence plasmid-encoded open reading frames (ORFs) (designated ORF3 and ORF4) exhibit significant identity with isoprenoid biosynthesis genes of Bacteria and Archaea. The predicted ORF4 product is closely related to isopentenyl isomerase (IDI) enzymes, whereas the predicted product of the adjacent ORF3 exhibits an aspartate-rich region that is common among trans-isoprenyl phosphate synthases. We show that mutations in these ORFs confer changes in bacterial surface properties. AggR coordinately controls expression of a large number of EAEC genes.

Modeling studies with Helicobacter pylori octaprenyl pyrophosphate synthase reveal the enzymatic mechanism of trans-prenyltransferases

Octaprenyl pyrophosphate synthase (OPPs), an enzyme belonging to the trans-prenyltransferases family, is involved in the synthesis of C40 octaprenyl pyrophosphate (OPP) by reacting farnesyl pyrophosphate (FPP) with five isopentenyl pyrophosphates (IPP). It has been reported that OPPs is essential for bacteria's normal growth and is a potential target for novel antibacterial drug design. Here we report the crystal structure of OPPs from Helicobacter pylori, determined by MAD method at 2.8 Å resolution and refined to 2.0 Å resolution. The substrate IPP was docked into HpOPPs structure and residues involved in IPP recognition were identified. The other substrate FPP, the intermediate GGPP and a nitrogen-containing bisphosphonate drug were also modeled into the structure. The resulting model shed some lights on the enzymatic mechanism, including (1) residues Arg87, Lys36 and Arg39 are essential for IPP binding; (2) residues Lys162, Lys224 and Gln197 are involved in FPP binding; (3) the second DDXXD motif may involve in FPP binding by Mg(2+) mediated interactions; (4) Leu127 is probably involved in product chain length determination in HpOPPs and (5) the intermediate products such as GGPP need a rearrange to occupy the binding site of FPP and then IPP is reloaded. Our results also indicate that the nitrogen-containing bisphosphonate drugs are potential inhibitors of FPPs and other trans-prenyltransferases aiming at blocking the binding of FPP.

Synthesis and NMR characterization of (Z,Z,Z,Z,E,E,ω)-heptaprenol

We describe a practical, multigram synthesis of (2Z,6Z,10Z,14Z,18E,22E)-3,7,11,15,19,23,27-heptamethyl-2,6,10,14,18,22,26-octacosaheptaen-1-ol [(Z(4),E(2),ω)-heptaprenol, 4] using the nerol-derived sulfone 8 as the key intermediate. Sulfone 8 is prepared by the literature route and is converted in five additional steps (18% yield from 8) to (Z(4),E(2),ω)-heptaprenol 4. The use of Eu(hfc)(3) as an NMR shift reagent not only enabled confirmation of the structure and stereochemistry of 4, but further enabled the structural assignment to a major side product from a failed synthetic connection. The availability by this synthesis of (Z(4),E(2),ω)-heptaprenol 4 in gram quantities will enable preparative access to key reagents for the study of the biosynthesis of the bacterial cell envelope.

Roles of amino acids in the Escherichia coli octaprenyl diphosphate synthase active site probed by structure-guided site-directed mutagenesis

Octaprenyl diphosphate synthase (OPPS) catalyzes consecutive condensation reactions of farnesyl diphosphate (FPP) with five molecules of isopentenyl diphosphates (IPP) to generate C(40) octaprenyl diphosphate, which constitutes the side chain of ubiquinone or menaquinone. To understand the roles of active site amino acids in substrate binding and catalysis, we conducted site-directed mutagenesis studies with Escherichia coli OPPS. In conclusion, D85 is the most important residue in the first DDXXD motif for both FPP and IPP binding through an H-bond network involving R93 and R94, respectively, whereas R94, K45, R48, and H77 are responsible for IPP binding by providing H-bonds and ionic interactions. K170 and T171 may stabilize the farnesyl carbocation intermediate to facilitate the reaction, whereas R93 and K225 may stabilize the catalytic base (MgPP(i)) for H(R) proton abstraction after IPP condensation. K225 and K235 in a flexible loop may interact with FPP when the enzyme becomes a closed conformation, which is therefore crucial for catalysis. Q208 is near the hydrophobic part of IPP and is important for IPP binding and catalysis.

Undecaprenyl diphosphate synthase, a cis-prenyltransferase synthesizing lipid carrier for bacterial cell wall biosynthesis

A group of prenyltransferases produce linear lipids by catalyzing consecutive condensation reactions of farnesyl diphosphate (FPP) with specific numbers of isopentenyl diphosphate (IPP), a common building block of isoprenoid compounds. Depending on the stereochemistry of the double bonds formed during IPP condensation, these prenyltransferases are categorized as cis- and trans-types. Undecaprenyl diphosphate synthase (UPPS) that catalyzes chain elongation of FPP by consecutive condensation reactions with eight IPP, to form C₅₅ lipid carrier for bacterial cell wall biosynthesis, serves as a model for understanding cis-prenyltransferases. In this review, the current knowledge in UPPS kinetics, mechanisms, structures, and inhibitors is summarized.

Isoprenoid biosynthesis in eukaryotic phototrophs: a spotlight on algae

Isoprenoids are one of the largest groups of natural compounds and have a variety of important functions in the primary metabolism of land plants and algae. In recent years, our understanding of the numerous facets of isoprenoid metabolism in land plants has been rapidly increasing, while knowledge on the metabolic network of isoprenoids in algae still lags behind. Here, current views on the biochemistry and genetics of the core isoprenoid metabolism in land plants and in the major algal phyla are compared and some of the most pressing open questions are highlighted. Based on the different evolutionary histories of the various groups of eukaryotic phototrophs, we discuss the distribution and regulation of the mevalonate (MVA) and the methylerythritol phosphate (MEP) pathways in land plants and algae and the potential consequences of the loss of the MVA pathway in groups such as the green algae. For the prenyltransferases, serving as gatekeepers to the various branches of terpenoid biosynthesis in land plants and algae, we explore the minimal inventory necessary for the formation of primary isoprenoids and present a preliminary analysis of their occurrence and phylogeny in algae with primary and secondary plastids. The review concludes with some perspectives on genetic engineering of the isoprenoid metabolism in algae.

Terpene biosynthesis: modularity rules

Terpenes are the largest class of small-molecule natural products on earth, and the most abundant by mass. Here, we summarize recent developments in elucidating the structure and function of the proteins involved in their biosynthesis. There are six main building blocks or modules (α, β, γ, δ, ε, and ζ) that make up the structures of these enzymes: the αα and αδ head-to-tail trans-prenyl transferases that produce trans-isoprenoid diphosphates from C(5) precursors; the ε head-to-head prenyl transferases that convert these diphosphates into the tri- and tetraterpene precursors of sterols, hopanoids, and carotenoids; the βγ di- and triterpene synthases; the ζ head-to-tail cis-prenyl transferases that produce the cis-isoprenoid diphosphates involved in bacterial cell wall biosynthesis; and finally the α, αβ, and αβγ terpene synthases that produce plant terpenes, with many of these modular enzymes having originated from ancestral α and β domain proteins. We also review progress in determining the structure and function of the two 4Fe-4S reductases involved in formation of the C(5) diphosphates in many bacteria, where again, highly modular structures are found.

Mechanism of cis-prenyltransferase reaction probed by substrate analogues

Undecaprenyl pyrophosphate synthase (UPPS) is a cis-type prenyltransferases which catalyzes condensation reactions of farnesyl diphosphate (FPP) with eight isopentenyl pyrophosphate (IPP) units to generate C(55) product. In this study, we used two analogues of FPP, 2-fluoro-FPP and [1,1-(2)H(2)]FPP, to probe the reaction mechanism of Escherichia coli UPPS. The reaction rate of 2-fluoro-FPP with IPP under single-turnover condition is similar to that of FPP, consistent with the mechanism without forming a farnesyl carbocation intermediate. Moreover, the deuterium secondary KIE of 0.985±0.022 measured for UPPS reaction using [1,1-(2)H(2)]FPP supports the associative transition state. Unlike the sequential mechanism used by trans-prenyltransferases, our data demonstrate E. coli UPPS utilizes the concerted mechanism.

Mechanism of dimethylallyltryptophan synthase: evidence for a dimethylallyl cation intermediate in an aromatic prenyltransferase reaction

Dimethylallyltryptophan synthase is an aromatic prenyltransferase that catalyzes an electrophilic aromatic substitution reaction between dimethylallyl diphosphate (DMAPP) and L-tryptophan. The synthase is found in a variety of fungi, where it catalyzes the first committed step in the biosynthesis of the ergot alkaloids. The enzymatic reaction could follow either a dissociative mechanism involving a discrete dimethylallyl cation intermediate or an associative mechanism in which the indole ring directly displaces diphosphate in a single step. In this work, positional isotope exchange (PIX) experiments are presented in support of a dissociative mechanism. When [1-(18)O]-DMAPP is subjected to the synthase reaction and recovered starting material is analyzed, 15% of the (18)O-label is found to have scrambled from a bridging to a nonbridging position on the alpha-phosphorus. Kinetic isotope effect studies show that steps involved in the formation of the arenium ion intermediate are rate-determining, and therefore the scrambling occurs during the lifetime of the dimethylallyl cation/diphosphate ion pair. Similarly, when the unreactive substrate analogue, 6-fluorotryptophan, was employed, complete scrambling of the (18)O-label in DMAPP was observed. To our knowledge, this is the first observation of PIX in any prenyltransferase reaction, and it provides strong evidence supporting the existence of a carbocation intermediate.

Reaction kinetics, catalytic mechanisms, conformational changes, and inhibitor design for prenyltransferases

Isoprenoids comprise a family of more than 55000 natural products with great structural variety derived from five-carbon isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). Allylic diphosphates such as farnesyl diphosphate (FPP) synthesized from DMAPP and IPP serve as outlet points for a great variety of products. A group of prenyltransferases catalyzing chain elongation of FPP to designated lengths by consecutive condensation reactions with specific numbers of IPP are classified as cis and trans types according to the stereochemistry of the double bonds formed by IPP condensation. The complete kinetics of the multistep IPP condensation reactions by both types of enzymes has been determined using steady-state and pre-steady-state approaches. Because their crystal structures were determined in conjunction with biochemical studies, a more thorough understanding of their catalytic mechanisms, protein conformational changes, and product chain-length determination mechanisms has been gained recently. Since these prenyltransferases play important roles, potent inhibitors have been identified and their cocrystal structures have been determined for drug development. In this review, the current knowledge of these prenyltransferases that synthesize prenyl oligomers or polymers is summarized.

Prenyl transfer to aromatic substrates: genetics and enzymology

Aromatic prenyltransferases catalyze the transfer of prenyl moieties to aromatic acceptor molecules and give rise to an astounding diversity of primary and secondary metabolites in plants, fungi and bacteria. Significant progress has been made in the biochemistry and genetics of this heterogeneous group of enzymes in the past years. After 30 years of extensive research on plant prenylflavonoid biosynthesis, finally the first aromatic prenyltransferases involved in the formation of these compounds have been cloned. In bacteria, investigations of the newly discovered family of ABBA prenyltransferases revealed a novel type of protein fold, the PT barrel. In fungi, a group of closely related indole prenyltransferase was found to carry out aromatic prenylations with different substrate specificity and regiospecificity, and to catalyze both regular and reverse prenylations.