Identification of soybean peptide leginsulin variants in different cultivars and their insulin-like activities.

We have recently reported that green soybean cultivar, echigomidori, and not the yellow cultivar, fukuyutaka, is a rich source of hormone-like peptide leginsulin consisting of 37 amino acids (Leg_1_37, PDB 1JU8A) and its C-terminal glycine deletant, Leg_1_36. Green soybean is mature, but the color of the seedcoat and cotyledon remains green. Therefore, in this study, we examined the leginsulin content in different varieties of 11 colored soybeans (including green, yellow, red, brown and black) and edamame (immature soybean). Profile analysis of soybean constituents by LC-MS showed that Leg_1 (36 + 37) detected as a prominent peak in 3 green and 1 yellow soybean cultivar was the strongest contributor in principal component analysis, indicating Leg_1 is the most characteristic feature for distinguishing soybean cultivars. However, smaller amounts of leginsulin-like peptides, defined as Leg_2 and Leg_3, were detected in other samples. The cDNA sequences and LC-MS/MS analyses revealed that Leg_2 was a homologue of Leg_1 with three amino acid substitutions derived from SNPs, while Leg_3 was a Leg_1/Leg_2 paralog. Expression levels of Leg_1 were markedly higher than Leg_2 and Leg_3. Additionally, in glucose uptake assay, purified TRX-His-tag fused recombinant Leg_1_37 prepared by bacterial expression showed stronger insulin-like activities than other variants including Leg_2, Leg_3, and their Gly deletants in myotube-like differentiated L6 and C2C12 cells. These results suggest that dietary consumption of soybean seed, especially including a higher amount of Leg_1_37, could be useful for lowering of blood glucose.

Computational Molecular Docking and X-ray Crystallographic Studies of Catechins in New Drug Design Strategies.

Epidemiological and laboratory studies have shown that green tea and green tea catechins exert beneficial effects on a variety of diseases, including cancer, metabolic syndrome, infectious diseases, and neurodegenerative diseases. In most cases, (-)-epigallocatechin gallate (EGCG) has been shown to play a central role in these effects by green tea. Catechins from other plant sources have also shown health benefits. Many studies have revealed that the binding of EGCG and other catechins to proteins is involved in its action mechanism. Computational docking analysis (CMDA) and X-ray crystallographic analysis (XCA) have provided detailed information on catechin-protein interactions. Several of these studies have revealed that the galloyl moiety anchors it to the cleft of proteins through interactions with its hydroxyl groups, explaining the higher activity of galloylated catechins such as EGCG and epicatechin gallate than non-galloylated catechins. In this paper, we review the results of CMDA and XCA of EGCG and other plant catechins to understand catechin-protein interactions with the expectation of developing new drugs with health-promoting properties.

In Vitro and In Silico Studies of the Molecular Interactions of Epigallocatechin-3-O-gallate (EGCG) with Proteins That Explain the Health Benefits of Green Tea.

Green tea has been shown to have beneficial effects on many diseases such as cancer, obesity, inflammatory diseases, and neurodegenerative disorders. The major green tea component, epigallocatechin-3-O-gallate (EGCG), has been demonstrated to contribute to these effects through its anti-oxidative and pro-oxidative properties. Furthermore, several lines of evidence have indicated that the binding affinity of EGCG to specific proteins may explain its mechanism of action. This review article aims to reveal how EGCG-protein interactions can explain the mechanism by which green tea/EGCG can exhibit health beneficial effects. We conducted a literature search, using mainly the PubMed database. The results showed that several methods such as dot assays, affinity gel chromatography, surface plasmon resonance, computational docking analyses, and X-ray crystallography have been used for this purpose. These studies have provided evidence to show how EGCG can fit or occupy the position in or near functional sites and induce a conformational change, including a quaternary conformational change in some cases. Active site blocking, steric hindrance by binding of EGCG near an active site or induced conformational change appeared to cause inhibition of enzymatic activity and other biological activities of proteins, which are related to EGCG's biological oligomer and formation of their toxic aggregates, leading to the prevention of neurodegenerative diseases and amyloidosis. In conclusion, these studies have provided useful information on the action of green tea/catechins and would lead to future studies that will provide further evidence for rational EGCG therapy and use EGCG as a lead compound for drug design.

Sulphur-containing compounds of durian activate the thermogenesis-inducing receptors TRPA1 and TRPV1.

Durian (Durio zibethinus Murr.) is classified as a body-warming food in Indian herbalism, and its hyperthermic effect is empirically known in Southeast Asia. To investigate the mechanism underlying this effect, we focused on the thermogenesis-inducing receptors, TRPA1 and TRPV1. Durian contains sulphides similar to the TRPA1 and TRPV1 agonists of garlic. Accordingly, we hypothesized that the thermogenic effect of durian is driven by sulphide-induced TRP channel activation. To investigate our hypothesis, we measured the TRPA1 and TRPV1 activity of the sulphur-containing components of durian and quantified their content in durian pulp. These sulphur-containing components had a stronger effect on TRPA1 than TRPV1. Furthermore, sulphide content in the durian pulp was sufficient to evoke TRP channel activation and the main agonist was diethyl disulphide. From these results, we consider that the body-warming effect of durian is elicited by TRPA1 activation with its sulphides, as can be seen in spices.

Trp-Arg-Xaa tripeptides act as uncompetitive-type inhibitors of human dipeptidyl peptidase IV.

Human dipeptidyl peptidase IV (hDPPIV, alternative name: CD26) inhibitors provide an effective strategy for the treatment of type 2 diabetes. Recently, our research group discovered a non substrate-mimic inhibitory dipeptide, Trp-Arg, by the systematic analysis of a dipeptide library. In the present study, a tripeptide library Trp-Arg-Xaa (where Xaa represents any amino acid) was analyzed to investigate the interactions of peptidergic inhibitors with hDPPIV. Trp-Arg-Glu showed the highest inhibitory effect toward hDPPIV (Ki=130 µM). All of the tested 19 Trp-Arg-Xaa tripeptides showed unique uncompetitive-type inhibition. The inhibition mechanism of Trp-Arg-Xaa is discussed based on the crystal structure of hDPPIV. The information obtained by this study suggests a novel concept for developing hDPPIV inhibitory peptides and drugs.