1
|
Deletti G, Green SD, Weber C, Patterson KN, Joshi SS, Khopade TM, Coban M, Veek-Wilson J, Caulfield TR, Viswanathan R, Lane AL. Unveiling an indole alkaloid diketopiperazine biosynthetic pathway that features a unique stereoisomerase and multifunctional methyltransferase. Nat Commun 2023; 14:2558. [PMID: 37137876 PMCID: PMC10156859 DOI: 10.1038/s41467-023-38168-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 04/19/2023] [Indexed: 05/05/2023] Open
Abstract
The 2,5-diketopiperazines are a prominent class of bioactive molecules. The nocardioazines are actinomycete natural products that feature a pyrroloindoline diketopiperazine scaffold composed of two D-tryptophan residues functionalized by N- and C-methylation, prenylation, and diannulation. Here we identify and characterize the nocardioazine B biosynthetic pathway from marine Nocardiopsis sp. CMB-M0232 by using heterologous biotransformations, in vitro biochemical assays, and macromolecular modeling. Assembly of the cyclo-L-Trp-L-Trp diketopiperazine precursor is catalyzed by a cyclodipeptide synthase. A separate genomic locus encodes tailoring of this precursor and includes an aspartate/glutamate racemase homolog as an unusual D/L isomerase acting upon diketopiperazine substrates, a phytoene synthase-like prenyltransferase as the catalyst of indole alkaloid diketopiperazine prenylation, and a rare dual function methyltransferase as the catalyst of both N- and C-methylation as the final steps of nocardioazine B biosynthesis. The biosynthetic paradigms revealed herein showcase Nature's molecular ingenuity and lay the foundation for diketopiperazine diversification via biocatalytic approaches.
Collapse
Affiliation(s)
- Garrett Deletti
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Sajan D Green
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Caleb Weber
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Kristen N Patterson
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
| | - Swapnil S Joshi
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
| | - Tushar M Khopade
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
| | - Mathew Coban
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - James Veek-Wilson
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Thomas R Caulfield
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, 32224, USA
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Rajesh Viswanathan
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA.
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India.
| | - Amy L Lane
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA.
| |
Collapse
|
2
|
Bearne SL, Hayden JA. Application of circular dichroism-based assays to racemases and epimerases: Recognition and catalysis of reactions of chiral substrates by mandelate racemase. Methods Enzymol 2023; 685:127-169. [PMID: 37245900 DOI: 10.1016/bs.mie.2023.03.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Racemases and epimerases have attracted much interest because of their astonishing ability to catalyze the rapid α-deprotonation of carbon acid substrates with high pKa values (∼13-30) leading to the formation of d-amino acids or various carbohydrate diastereomers that serve important roles in both normal physiology and pathology. Enzymatic assays to measure the initial rates of reactions catalyzed by these enzymes are discussed using mandelate racemase (MR) as an example. For MR, a convenient, rapid, and versatile circular dichroism (CD)-based assay has been used to determine the kinetic parameters accompanying the MR-catalyzed racemization of mandelate and alternative substrates. This direct, continuous assay permits real time monitoring of reaction progress, the rapid determination of initial velocities, and immediate recognition of anomalous behaviors. MR recognizes chiral substrates primarily through interactions of the phenyl ring of (R)- or (S)-mandelate with the hydrophobic R- or S-pocket at the active site, respectively. During catalysis, the carboxylate and α-hydroxyl groups of the substrate remain fixed in place through interactions with the Mg2+ ion and multiple H-bonding interactions, while the phenyl ring moves between the R- and S-pockets. The minimal requirements for the substrate appear to be the presence of a glycolate or glycolamide moiety, and a hydrophobic group of limited size that can stabilize the carbanionic intermediate through resonance or strong inductive effects. Similar CD-based assays may be applied to determine the activity of other racemases or epimerases with proper consideration of the molar ellipticity, wavelength, overall absorbance of the sample, and the light pathlength.
Collapse
Affiliation(s)
- Stephen L Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada; Department of Chemistry, Dalhousie University, Halifax, NS, Canada.
| | - Joshua A Hayden
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
| |
Collapse
|
3
|
Bearne SL. Through the Looking Glass: Chiral Recognition of Substrates and Products at the Active Sites of Racemases and Epimerases. Chemistry 2020; 26:10367-10390. [DOI: 10.1002/chem.201905826] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/09/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Stephen L. Bearne
- Department of Biochemistry & Molecular BiologyDepartment of ChemistryDalhousie University Halifax, Nova Scotia B3H 4R2 Canada
| |
Collapse
|
4
|
Marchetti M, Ronda L, Percudani R, Bettati S. Immobilization of Allantoinase for the Development of an Optical Biosensor of Oxidative Stress States. SENSORS 2019; 20:s20010196. [PMID: 31905788 PMCID: PMC6983136 DOI: 10.3390/s20010196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 12/23/2019] [Accepted: 12/27/2019] [Indexed: 02/04/2023]
Abstract
Allantoin, the natural end product of purine catabolism in mammals, is non-enzymatically produced from the scavenging of reactive oxygen species through the degradation of uric acid. Levels of allantoin in biological fluids are sensitively influenced by the presence of free radicals, making this molecule a candidate marker of acute oxidative stress in clinical analyses. With this aim, we exploited allantoinase—the enzyme responsible for allantoin hydrolization in plants and lower organisms—for the development of a biosensor exploiting a fast enzymatic-chemical assay for allantoin quantification. Recombinant allantoinase was entrapped in a wet nanoporous silica gel matrix and its structural properties, function, and stability were characterized through fluorescence spectroscopy and circular dichroism measurements, and compared to the soluble enzyme. Physical immobilization in silica gel minimally influences the structure and the catalytic efficiency of entrapped allantoinase, which can be reused several times and stored for several months with good activity retention. These results, together with the relative ease of the sol-gel preparation and handling, make the encapsulated allantoinase a good candidate for the development of an allantoin biosensor.
Collapse
Affiliation(s)
- Marialaura Marchetti
- Centro Interdipartimentale Biopharmanet-TEC, Università di Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy; (M.M.); (S.B.)
| | - Luca Ronda
- Centro Interdipartimentale Biopharmanet-TEC, Università di Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy; (M.M.); (S.B.)
- Dipartimento di Medicina e Chirurgia, Università di Parma, Via Gramsci 14, 43126 Parma, Italy
- Correspondence: ; Tel.: +39-0521-905502
| | - Riccardo Percudani
- Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Via Parco Area delle Scienze 11/A, 43124 Parma, Italy;
| | - Stefano Bettati
- Centro Interdipartimentale Biopharmanet-TEC, Università di Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy; (M.M.); (S.B.)
- Dipartimento di Medicina e Chirurgia, Università di Parma, Via Gramsci 14, 43126 Parma, Italy
| |
Collapse
|