Substrate-Multiplexed Assessment of Aromatic Prenyltransferase Activity

An increasingly effective strategy to identify synthetically useful enzymes is to sample the diversity already present in Nature. Here, we construct and assay a panel of phylogenetically diverse aromatic prenyltransferases (PTs). These enzymes catalyze a variety of C-C bond forming reactions in natural product biosynthesis and are emerging as tools for synthetic chemistry and biology. Homolog screening was further empowered through substrate-multiplexed screening, which provides direct information on enzyme specificity. We perform a head-to-head assessment of the model members of the PT family and further identify homologs with divergent sequences that rival these superb enzymes. This effort revealed the first bacterial O-Tyr PT and, together, provide valuable benchmarking for future synthetic applications of PTs.

Structural insights into the diverse prenylating capabilities of DMATS prenyltransferases

Covering: 2009 up to August 2023Prenyltransferases (PTs) are involved in the primary and the secondary metabolism of plants, bacteria, and fungi, and they are key enzymes in the biosynthesis of many clinically relevant natural products (NPs). The continued biochemical and structural characterization of the soluble dimethylallyl tryptophan synthase (DMATS) PTs over the past two decades have revealed the significant promise that these enzymes hold as biocatalysts for the chemoenzymatic synthesis of novel drug leads. This is a comprehensive review of DMATSs describing the structure-function relationships that have shaped the mechanistic underpinnings of these enzymes, as well as the application of this knowledge to the engineering of DMATSs. We summarize the key findings and lessons learned from these studies over the past 14 years (2009-2023). In addition, we identify current gaps in our understanding of these fascinating enzymes.

Structure-guided Mutagenesis Reveals the Catalytic Residue that Controls the Regiospecificity of C6-Indole Prenyltransferases

Indole is a significant structural moiety and functionalization of the C-H bond in indole-containing molecules expands their chemical space, and modifies their properties and/or activities. Indole prenyltransferases (IPTs) catalyze the direct regiospecific installation of prenyl, C5 carbon units, on indole-derived compounds. IPTs have shown relaxed substrate flexibility enabling them to be used as tools for indole functionalization. However, the mechanism by which certain IPTs target a specific carbon position is not fully understood. Herein, we use structure-guided site-directed mutagenesis, in vitro enzymatic reactions, kinetics and structural-elucidation of analogs to verify the key catalytic residues that control the regiospecificity of all characterized regiospecific C6 IPTs. Our results also demonstrate that substitution of PriB_His312 to Tyr leads to the synthesis of analogs prenylated at different positions than C6. This work contributes to understanding of how certain IPTs can access a challenging position in indole-derived compounds.

Prenylation: A Critical Step for Biomanufacturing of Prenylated Aromatic Natural Products

Prenylated aromatic natural products (PANPs) have received much attention due to their biomedical benefits for human health. The prenylation of aromatic natural products (ANPs), which is mainly catalyzed by aromatic prenyltransferases (aPTs), contributes significantly to their structural and functional diversity by providing higher lipophilicity and enhanced bioactivity. aPTs are widely distributed in bacteria, fungi, animals, and plants and play a key role in the regiospecific prenylation of ANPs. Recent studies have greatly advanced our understanding of the characteristics and application of aPTs. In this review, we comment on research progress regarding sources, evolutionary relationships, structural features, reaction mechanism, engineering modification, and application of aPTs. Particular emphasis is also placed on recent advances, challenges, and prospects about applications of aPTs in microbial cell factories for producing PANPs. Generally, this review could provide guidance for using aPTs as robust biocatalytic tools to produce various PANPs with high efficiency.

Integrative transcriptome analysis revealed the pathogenic molecular basis of Rhizoctonia solani AG-3 TB at three progressive stages of infection

Rhizoctonia solani has a broad host range and results in significant losses in agricultural production. Here, an integrated transcriptomic analysis was performed to reveal the critical genes responsible for the pathogenesis of R. solani AG-3 TB on Nicotiana tabacum at different infection stages. The results showed that various differential expressed genes (DEGs) were enriched in fatty acid metabolism, amino sugar, carbon metabolism, and cellular carbohydrate biosynthetic process at the early (6–12 hpi), middle (24–36 hpi), and late stage (48–72 hpi) of infection. Specifically, several critical genes such as shikimate kinase that were involved in the biosynthesis of an important fungal toxin, phenylacetic acid (PAA) showed markedly increase at 24 hpi. Additionally, the genes expression levels of carbohydrate-active enzymes (CAZymes) and cell wall degrading enzymes (CWDEs) were significantly increased at the late infection stage. Furthermore, we identified 807 potential secreted proteins and 78 small cysteine-rich proteins, which may function as fungal effectors and involved in the pathogenicity. These results provide valuable insights into critical and potential genes as well as the pathways involved in the pathogenesis of R. solani AG-3 TB.

Reprogramming Substrate and Catalytic Promiscuity of Tryptophan Prenyltransferases

Prenylation is a process widely prevalent in primary and secondary metabolism, contributing to functionality and chemical diversity in natural systems. Due to their high regio- and chemoselectivities, prenyltransferases are also valuable tools for creation of new compounds by chemoenzymatic synthesis and synthetic biology. Over the last ten years, biochemical and structural investigations shed light on the mechanism and key residues that control the catalytic process, but to date crucial information on how certain prenyltransferases control regioselectivity and chemoselectivity is still lacking. Here, we advance a general understanding of the enzyme family by contributing the first structure of a tryptophan C5-prenyltransferase 5-DMATS. Additinally, the structure of a bacterial tryptophan C6-prenyltransferase 6-DMATS was solved. Analysis and comparison of both substrate-bound complexes led to the identification of key residues for catalysis. Next, site-directed mutagenesis was successfully implemented to not only modify the prenyl donor specificity but also to redirect the prenylation, thereby switching the regioselectivity of 6-DMATS to that of 5-DMATS. The general strategy of structure-guided protein engineering should be applicable to other related prenyltransferases, thus enabling the production of novel prenylated compounds.

Biochemical and Mechanistic Characterization of the Fungal Reverse N-1-Dimethylallyltryptophan Synthase DMATS1Ff

Dimethylallyltryptophan synthases catalyze the regiospecific transfer of (oligo)prenylpyrophosphates to aromatic substrates like tryptophan derivatives. These reactions are key steps in many biosynthetic pathways of fungal and bacterial secondary metabolites. In vitro investigations on recombinant DMATS1_Ff from Fusarium fujikuroi identified the enzyme as the first selective reverse tryptophan-N-1 prenyltransferase of fungal origin. The enzyme was also able to catalyze the reverse N-geranylation of tryptophan. DMATS1_Ff was shown to be phylogenetically related to fungal tyrosine O-prenyltransferases and fungal 7-DMATS. Like these enzymes, DMATS1_Ff was able to convert tyrosine into its regularly O-prenylated derivative. Investigation of the binding sites of DMATS1_Ff by homology modeling and comparison to the crystal structure of 4-DMATS FgaPT2 showed an almost identical site for DMAPP binding but different residues for tryptophan coordination. Several putative active site residues were verified by site directed mutagenesis of DMATS1_Ff. Homology models of the phylogenetically related enzymes showed similar tryptophan binding residues, pointing to a unified substrate binding orientation of tryptophan and DMAPP, which is distinct from that in FgaPT2. Isotopic labeling experiments showed the reaction catalyzed by DMATS1_Ff to be nonstereospecific. Based on these data, a detailed mechanism for DMATS1_Ff catalysis is proposed.