Elicitor-induced rosmarinic acid accumulation and secondary metabolism enzyme activities in Solenostemon scutellarioides

This study aimed to improve rosmarinic acid (RA) production in the whole plant culture of Solenostemon scutellarioides through elicitation. Amongst selected elicitors methyl jasmonate (MJ), salicylic acid (SA), and yeast extract (YE) caused significant elevation in RA accumulation. Elicitation with MJ (50 μM) and SA (50 μM) caused almost 1.7 and 1.4-fold increase in RA accumulation, respectively, within day 1. While YE (100 μg ml^?1) elicitation showed highest RA content (~1.5-fold) in day 3. Preceding the elicitor-induced RA accumulation, there was a notable alteration in the specific activities of RA biosynthetic enzymes viz. phenylalanine ammonia lyase, tyrosine aminotransferase, hydroxyl-phenylpyruvate reductase and rosmarinic acid synthase up on MJ (50 μM), SA (50 μM) and YE (100 mg ml^?1) elicitation. Based on differential responses of aforementioned enzymes, RA synthesis was further scaled up through combination of elicitors in pre-optimized doses. In synergy study, at a time exposure with MJ + SA + YE and MJ + SA followed by YE after 24 h has been found to produce significant elevation of RA (2.0 and 1.9-fold, respectively) within 24 h while later maintained a steady state increased level (~1.7 ± 0.2-fold) over control up to day 7.     

(3R)-4-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-(2,2,2-trifluoroethyl)-1,4-diazepan-2-one, a selective dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes

Replacement of the triazolopiperazine ring of sitagliptin (DPP-4 IC(50)=18nM) with 3-(2,2,2-trifluoroethyl)-1,4-diazepan-2-one gave dipeptidyl peptidase IV (DPP-4) inhibitor 1 which is potent (DPP-4 IC(50)=2.6nM), selective, and efficacious in an oral glucose tolerance test in mice. It was selected for extensive preclinical development as a potential back-up candidate to sitagliptin.     

Modeling assisted rational design of novel, potent, and selective pyrrolopyrimidine DPP-4 inhibitors

Molecular modeling was used to improve potency of the cyclohexylamine series. In addition, a 3-D QSAR method was used to gain insight for reducing off-target DPP-8/9 activities. Compounds 3, 4, and 5 were synthesized and found to be potent DPP-4 inhibitors, in particular 4 and 5 are designed to be highly selective against off-target DASH enzymes while maintaining potency on DPP-4.     

Rational design of a novel, potent, and orally bioavailable cyclohexylamine DPP-4 inhibitor by application of molecular modeling and X-ray crystallography of sitagliptin

Molecular modeling was used to design a rigid analog of sitagliptin 1. The X-ray crystal structure of sitagliptin bound to DPP-4 suggested that the central beta-amino butyl amide moiety could be replaced with a cyclohexylamine group. This was confirmed by structural analysis and the resulting analog 2a was synthesized and found to be a potent DPP-4 inhibitor (IC(50)=21 nM) with excellent in vivo activity and pharmacokinetic profile.     

Discovery of benzodihydroisofurans as novel, potent, bioavailable and brain-penetrant prolylcarboxypeptidase inhibitors

A series of benzodihydroisofurans were discovered as novel, potent, bioavailable and brain-penetrant prolylcarboxypeptidase (PrCP) inhibitors. The structure-activity relationship (SAR) is focused on improving PrCP activity and metabolic stability, and reducing plasma protein binding. In the established diet-induced obese (eDIO) mouse model, compound ent-3a displayed target engagement both in plasma and in brain. However, this compound failed to induce significant body weight loss in eDIO mice in a five-day study.     

Observing a late folding intermediate of Ubiquitin at atomic resolution by NMR

The study of intermediates in the protein folding pathway provides a wealth of information about the energy landscape. The intermediates also frequently initiate pathogenic fibril formations. While observing the intermediates is difficult due to their transient nature, extreme conditions can partially unfold the proteins and provide a glimpse of the intermediate states. Here, we observe the high resolution structure of a hydrophobic core mutant of Ubiquitin at an extreme acidic pH by nuclear magnetic resonance (NMR) spectroscopy. In the structure, the native secondary and tertiary structure is conserved for a major part of the protein. However, a long loop between the beta strands β3 and β5 is partially unfolded. The altered structure is supported by fluorescence data and the difference in free energies between the native state and the intermediate is reflected in the denaturant induced melting curves. The unfolded region includes amino acids that are critical for interaction with cofactors as well as for assembly of poly‐Ubiquitin chains. The structure at acidic pH resembles a late folding intermediate of Ubiquitin and indicates that upon stabilization of the protein's core, the long loop converges on the core in the final step of the folding process.     

Promiscuous Interactions of gp78 E3 Ligase CUE Domain with Polyubiquitin Chains

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Highlights? The ubiquitin ligase gp78 recruits ubiquitinated substrates via its CUE domain ? gp78CUE:Ub complex reveals a large set of specific interactions ? gp78CUE binds to both distal and proximal moities of diubiquitin in a similar fashion ? The gp78CUE domain binds to K48- and K63-linked diubiquitin equally well     

Aminopiperidine-fused imidazoles as dipeptidyl peptidase-IV inhibitors

A new series of DPP-4 inhibitors derived from piperidine-fused benzimidazoles and imidazopyridines is described. Optimization of this class of DPP-4 inhibitors led to the discovery of imidazopyridine 34. The potency, selectivity, cross-species DMPK profiles, and in vivo efficacy of 34 is reported.