Sulphostin, a potent inhibitor for dipeptidyl peptidase IV from Streptomyces sp. MK251-43F3

Recent advances in the synthesis and applications of phosphoramides

Phosphoramide, as an important framework of many biologically active molecules, has attracted widespread attention in recent decades. It is not only widely used in pharmaceuticals because of its excellent biological activities, but it also shows good performance in organic dyes, flame retardants and extractors. Thus, it is of great significance to develop effective and convenient methods for the synthesis of phosphoramides. In this review, the recent advancements made in the synthesis routes and applications of phosphoramides are discussed. The synthetic strategies of phosphoramides can be separated into five categories: phosphorus halides as the substrate, phosphates as the substrate, phosphorus hydrogen as the substrate, azides as the substrate and other methods. The latest examples of these methods are provided and some representative mechanisms are also described.

Biosynthesis of sulfonamide and sulfamate antibiotics in actinomycete

Sulfonamides and sulfamates are a group of organosulfur compounds that contain the signature sulfamoyl structural motif. These compounds were initially only known as synthetic antibacterial drugs but were later also discovered as natural products. Eight highly potent examples have been isolated from actinomycetes to date, illustrating the large biosynthetic repertoire of this bacterial genus. For the biosynthesis of these compounds, several distinct and unique biosynthetic machineries have been discovered, capable to generate the unique S–N bond. For the creation of novel, second generation natural products by biosynthetic engineering efforts, a detailed understanding of the underlying enzyme machinery toward potent structural motifs is crucial. In this review, we aim to summarize the current state of knowledge on sulfonamide and sulfamate biosynthesis. A detailed discussion for the secondary sulfamate ascamycin, the tertiary sulfonamide sulfadixiamycin A, and the secondary sulfonamide SB-203208 is provided and their bioactivities and mode of actions are discussed.

Natural Products Containing a Nitrogen-Sulfur Bond

Only about 100 natural products are known to contain a nitrogen-sulfur (N-S) bond. This review thoroughly categorizes N-S bond-containing compounds by structural class. Information on biological source, biological activity, and biosynthesis is included, if known. We also review the role of N-S bond functional groups as post-translational modifications of amino acids in proteins and peptides, emphasizing their role in the metabolism of the cell.

Identification of novel human dipeptidyl peptidase-IV inhibitors of natural origin (part I): virtual screening and activity assays

Background

There has been great interest in determining whether natural products show biological activity toward protein targets of pharmacological relevance. One target of particular interest is DPP-IV whose most important substrates are incretins that, among other beneficial effects, stimulates insulin biosynthesis and secretion. Incretins have very short half-lives because of their rapid degradation by DPP-IV and, therefore, inhibiting this enzyme improves glucose homeostasis. As a result, DPP-IV inhibitors are of considerable interest to the pharmaceutical industry. The main goals of this study were (a) to develop a virtual screening process to identify potential DPP-IV inhibitors of natural origin; (b) to evaluate the reliability of our virtual-screening protocol by experimentally testing the in vitro activity of selected natural-product hits; and (c) to use the most active hit for predicting derivatives with higher binding affinities for the DPP-IV binding site.

Methodology/Principal Findings

We predicted that 446 out of the 89,165 molecules present in the natural products subset of the ZINC database would inhibit DPP-IV with good ADMET properties. Notably, when these 446 molecules were merged with 2,342 known DPP-IV inhibitors and the resulting set was classified into 50 clusters according to chemical similarity, there were 12 clusters that contained only natural products for which no DPP-IV inhibitory activity has been previously reported. Nine molecules from 7 of these 12 clusters were then selected for in vitro activity testing and 7 out of the 9 molecules were shown to inhibit DPP-IV (where the remaining two molecules could not be solubilized, preventing the evaluation of their DPP-IV inhibitory activity). Then, the hit with the highest activity was used as a lead compound in the prediction of more potent derivatives.

Conclusions/Significance

We have demonstrated that our virtual-screening protocol was successful in identifying novel lead compounds for developing more potent DPP-IV inhibitors.

Sulphostin, a novel inhibitor of dipeptidyl peptidases IV (DPPIV) that stimulates hematopoiesis in mice

CD26, a membrane-bound ectopeptidase, is known as an activated T cell marker with dipeptidyl peptidase IV (DPPIV) activity that has diverse functional roles in the regulation of peptide hormones, neuropeptides, chemokines and growth factors. We recently isolated a novel inhibitor of DPPIV, sulphostin, from culture broth of Streptomyces sp. MK251-43F3. We investigated herein the hematopoietic effect of sulphostin in mice and found that sulphostin induced the production of granulocyte colony-stimulating factor (G-CSF), stimulated myeloblasts in bone marrow, and increased neutrophil numbers in peripheral blood in both normal mice and mice with cyclophosphamide-induced leucopenia. Sulphostin desulfonate, in addition to sulphostin, has a similar inhibitory effect on DPPIV and stimulatory effect on neutrophils. These results suggest that DPPIV/CD26 might be a novel target for hematopoietic stimulation and DPPIV inhibitors including sulphostin and derivatives may be candidates for further development.

Synthesis and biological activity of sulphostin analogues, novel dipeptidyl peptidase IV inhibitors

The structure of sulphostin (1), a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, is consisted of three key functional groups, including a characteristic amino(sulfoamino)phosphinyl group, on a piperidine ring. To examine the relationship between its structure and the inhibitory activity against DPP-IV, various analogues were synthesized and their activities were investigated. These results indicated that all of the functional groups on the piperidine ring were crucial to the DPP-IV inhibitory activity of sulphostin, and that the sulfonic acid group, which constructed the amino(sulfoamino)phosphinyl group, contributed to the stability of the compound. Moreover, those functional groups should be adjoined on the piperidine ring for the inhibitory activity. The size of the nitrogen-containing heterocyclic ring including piperidine appeared to scarcely affect the activity. In the present study, the sulfonic acid-deficient five-membered ring analogue 27a showed the strongest inhibitory activity (IC50=11 nM).

First synthesis and determination of the absolute configuration of sulphostin, a novel inhibitor of dipeptidyl peptidase IV

Sulphostin, a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, was isolated from the culture broth of Streptomyces sp. MK251-43F3. Determination of the absolute configurations of two asymmetric atoms using the natural product was not achieved due to the small amount of the compound obtained. We synthesized four possible stereoisomers of sulphostin from D- or L-ornithine and compared their physicochemical and biological data to naturally isolated sulphostin. As a result, the absolute configurations at C-3 and the phosphorus atom of sulphostin were determined to be S and R, respectively, by X-ray crystallography. Synthetic sulphostin and its C-3 epimer have strong inhibitory activities against DPP-IV, IC50 values of which are 6.0 and 8.9 ng/mL, respectively. Thus it appears that the configuration of the phosphorus atom is primarily responsible for the activity; in contrast, the configuration of C-3 does not appear to affect the activity.