Backbone resonance assignments of the C-terminal thioesterase domain of tyrocidine synthetase C.

Natural macrocyclic peptides produced by microorganisms serve as valuable resources for therapeutic compounds, including antibiotics, anticancer agents, and immune suppressive agents. Nonribosomal peptide synthetases (NRPSs) are responsible for the biosynthesis of macrocyclic peptides. NRPSs are large multimodular enzymes, and each module recognizes and incorporates one specific amino acid into the polypeptide product.

Discovery of a Pentapeptide Antagonist to Human Neuromedin U Receptor 1.

Neuromedin U (NMU) activates two types of receptors (NMUR1 and NMUR2), and the former is mainly expressed in the peripheral tissues, including the intestinal tract and lung tissues. Since NMUR1 contributes to the promotion of type 2 inflammation in these tissues, it is a potential target to suppress inflammatory responses. However, promising antagonist candidates for human NMUR1 have not yet been developed.

Detection of Active SARS-CoV-2 3CL Protease in Infected Cells Using Activity-Based Probes with a 2,6-Dichlorobenzoyloxymethyl Ketone Reactive Warhead.

The 3CL protease (3CLpro) is a viral cysteine protease of SARS-CoV-2 and is responsible for the main processing of the viral polyproteins involved in viral replication and proliferation. Despite the importance of 3CLpro as a drug target, the intracellular dynamics of active 3CLpro, including its expression and subcellular localization in SARS-CoV-2-infected cells, are poorly understood. Herein, we report an activity-based probe (ABP) with a clickable alkyne and an irreversible warhead for the SARS-CoV-2 3CL protease.

Development of Conformationally Restricted Negamycin Derivatives for Potent Readthrough Activity.

(+)-Negamycin, which is a dipeptide-like antibiotic containing a hydrazide structure, exhibits readthrough activity, resulting in the restoration of dystrophin in the mouse model of Duchenne muscular dystrophy (DMD). In our previous structure-activity relationship study of negamycin, we found that its natural analogue 3--deoxynegamycin (TCP-107), without antimicrobial activity, showed a higher readthrough activity than negamycin. In this study, we designed and synthesized cyclopropane-based conformationally restricted derivatives of TCP-107 and evaluated their readthrough activity in the cell-based reporter assay against a TGA-type mutation derived from DMD.

[Development of Synthetic Methodology for Mid-size Peptide Based on Disulfide Bond Formation].

Disulfide bonds in peptides contribute to the immobilization and rigidity of their structures, leading to the expression of biological activity and resistance to metabolic enzymes. In addition, disulfide bonds are important in the construction of conjugates comprising two bioactive molecules such as peptides, sugars and drugs. Therefore, new methods of disulfide bond formation contribute to a more efficient construction of disulfide products.

Peptide mixed phosphonates for covalent complex formation with thioesterases in nonribosomal peptide synthetases.

Natural macrocyclic peptides derived from microorganisms are medicinal resources that are important for the development of new therapeutic agents. Most of these molecules are biosynthesized by a nonribosomal peptide synthetase (NRPS). The thioesterase (TE) domain in NRPS is responsible for the macrocyclization of mature linear peptide thioesters in a final biosynthetic step.

X-Ray Conformation and Structure-Activity Relationships of MA026, a Reversible Tight Junction Opener.

MA026, a cyclic lipodepsipeptide, opens the tight junction (TJ) probably via binding to claudin-1. We reported that (1) TJ-opening activity is dependent on the amino acid sequence order at Glu10-Leu11; (2) an epimer at the C3 position of the -terminal acyl tail decreased the TJ-opening activity; and (3) the epimers D-Leu1/L-Gln6 and L-Leu1/D-Gln6 showed more potent TJ-opening activity than natural MA026, although no systematic structure-activity relationship (SAR) study was conducted. Here, we report the three-dimensional structure and systematic SAR study of MA026.

Development of a novel fluorogenic assay method for screening inhibitors of bovine leukemia virus protease and identification of mitorubrinic acid as an anti-BLV compound.

Bovine leukemia virus (BLV) causes enzootic bovine leukosis, a fatal cattle disease that leads to significant economic losses in the livestock industry. Currently, no effective BLV countermeasures exist, except testing and culling. In this study, we developed a high-throughput fluorogenic assay to evaluate the inhibitory activity of various compounds on BLV protease, an essential enzyme for viral replication.

Establishment of One-Pot Disulfide-Driven Cyclic Peptide Synthesis with a 3-Nitro-2-pyridinesulfenate.

We have developed a new one-pot disulfide-driven cyclic peptide synthesis. The entire process is carried out in the solid phase, thus eliminating complicated work up procedures to remove by-products and unreacted reagents and enabling production of high-purity cyclic disulfide peptides by simple cleavage of a peptidyl resin. The one-pot synthesis of oxytocin was accomplished in this way with an isolated yield of 28% over 13 steps.

Inactivation of myostatin by photooxygenation using functionalized d-peptides.

Inhibition of myostatin is an attractive strategy for the treatment of muscular atrophic diseases such as muscular dystrophy. For the efficient inhibition of myostatin, functionalized peptides were developed by the conjugation of a 16-mer myostatin-binding d-peptide with a photooxygenation catalyst. These peptides induced myostatin-selective photooxygenation and inactivation under near-infrared irradiation, and were associated with little cytotoxicity or phototoxicity.

Influence of novel readthrough agents on myelin protein zero translation in the peripheral nervous system.

Translational readthrough-inducing agents have been developed for the treatment of nonsense mutations in hereditary diseases. The clinical effectiveness of readthrough agents has been reported, although newly developed agents are still desired because of their toxicities or limited clinical effectiveness. Recently, novel negamycin-derived readthrough agents without antimicrobial activity have been developed.

3CL Protease Inhibitors with an Electrophilic Arylketone Moiety as Anti-SARS-CoV-2 Agents.

The novel coronavirus, SARS-CoV-2, has been identified as the causative agent for the current coronavirus disease (COVID-19) pandemic. 3CL protease (3CL) plays a pivotal role in the processing of viral polyproteins. We report peptidomimetic compounds with a unique benzothiazolyl ketone as a warhead group, which display potent activity against SARS-CoV-2 3CL.

Strategic structure-activity relationship study on a follistatin-derived myostatin inhibitory peptide.

Myostatin, a negative regulator of muscle mass is a promising target for the treatment of muscle atrophic diseases. The novel myostatin inhibitory peptide, DF-3 is derived from the N-terminal α-helical domain of follistatin, which is an endogenous inhibitor of myostatin and other TGF-β family members. It has been suggested that the optimization of hydrophobic residues is important to enhance the myostatin inhibition.

Development of a High-Affinity Antibody-Binding Peptide for Site-Specific Modification.

Immunoglobulin G (IgG)-binding peptides such as 15-IgBP are convenient tools for the site-specific modification of antibodies and the preparation of homogeneous antibody-drug conjugates. A peptide such as 15-IgBP can be selectively crosslinked to the fragment crystallizable region of human IgG in an affinity-dependent manner via the ϵ-amino group of Lys8. Previously, we found that the peptide 15-Lys8Leu has a high affinity (K =8.

Structural Revision of Natural Cyclic Depsipeptide MA026 Established by Total Synthesis and Biosynthetic Gene Cluster Analysis.

A revised structure of natural 14-mer cyclic depsipeptide MA026, isolated from Pseudomonas sp. RtlB026 in 2002 was established by physicochemical analysis with HPLC, MS/MS, and NMR and confirmed by total solid-phase synthesis. The revised structure differs from that previously reported in that two amino acid residues, assigned in error, have been replaced.

Development of functionalized peptides for efficient inhibition of myostatin by selective photooxygenation.

For the inhibition of myostatin, which is an attractive strategy for the treatment of muscle atrophic disorders including muscular dystrophy, myostatin-binding peptides were synthesized with an on/off-switchable photooxygenation catalyst at different positions on the peptide chain. These functionalized peptides oxygenated and inactivated myostatin upon irradiation with near-infrared light. Among the peptides tested, a peptide (5) with the catalyst moiety at the 16 position induced myostatin-selective photooxygenation, and efficiently inhibited myostatin.

Use of solid-supported 4-fluorophenyl 3-nitro-2-pyridinesulfenate in the construction of disulfide-linked hybrid molecules.

To construct disulfide-linked hybrid molecules systematically and efficiently, we established a more practical solid-phase disulfide ligation (SPDSL) system with enhanced utility. The group Npys-OPh(pF) shows reactivity similar to that of Npys-Cl, but it is more stable. An efficient synthesis of the cyclic peptide oxytocin and a peptide-sugar conjugate was accomplished as models.

Design and synthesis of peptidic partial agonists of human neuromedin U receptor 1 with enhanced serum stability.

Neuromedin U (NMU) activates two receptors (NMUR1 and NMUR2) and is a promising candidate for development of drugs to combat obesity. Previously, we obtained hexapeptides as selective full NMUR agonists. Development of a partial agonist which mildly activates receptors is an effective strategy which lead to an understanding of the functions of NMU receptors.

Enzymatic Stability of Myostatin Inhibitory 16-mer Peptides.

Inhibition of myostatin is a promising strategy for treatment of muscle atrophic disorders. A 16-mer myostatin inhibitory linear peptide, MIPE-1686, administered intramuscularly, significantly increases muscle mass and hindlimb grip strength in Duchenne muscular dystrophic model mice. In this paper, we describe our examination of the enzymatic stabilities of this peptide with recombinant human proteases, aminopeptidase N, chymotrypsin C, and trypsin 3.

A chemically stable peptide agonist to neuromedin U receptor type 2.

Neuromedin U (NMU) is a peptide with appetite suppressive activity and other physiological activities via activation of the NMU receptors NMUR1 and NMUR2. In 2014, we reported the first NMUR2 selective agonist, 3-cyclohexylpropionyl-Leu-Leu-Dap-Pro-Arg-Asn-NH (CPN-116). However, we found that CPN-116 in phosphate buffer is unstable because of N-to-N acyl migration at the Dap residue.

In vitro simultaneous mapping of the partial pressure of oxygen, pH and inorganic phosphate using electron paramagnetic resonance.

The partial pressure of oxygen (pO) and the extracellular pH in the tumour microenvironment are essential parameters for understanding the physiological state of a solid tumour. Also, phosphate-containing metabolites are involved in energy metabolism, and interstitial inorganic phosphate (Pi) is an informative marker for tumour growth. This article describes the simultaneous mapping of pO, pH and Pi using 750 MHz continuous-wave (CW) electron paramagnetic resonance (EPR) and a multifunctional probe, monophosphonated trityl radical pTAM-D.

Discovery of a follistatin-derived myostatin inhibitory peptide.

Follistatin is well known as an inhibitor of transforming growth factor (TGF)-β superfamily ligands including myostatin and activin A. Myostatin, a negative regulator of muscle growth, is a promising target with which to treat muscle atrophic diseases. Here, we focused on the N-terminal domain (ND) of follistatin (Fst) that interacts with the type I receptor binding site of myostatin.