In silico identification of natural product inhibitors for γ-secretase activating protein,a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD) is clinically characterized by the aggregation of neurotoxic amyloid-β (Aβ) peptides in the brain. γ-Secretase catalyzes the reaction of Aβ formation. Inhibition of γ-secretase activating protein (GSAP) reduces Aβ production without disrupting other molecular functions and serves as a promising therapeutic target for lowering Aβ and curing AD. Till date, no proven drug is available for curing AD because of the nonexistence of crystal/NMR structure of GSAP. Thus in the present study, for the first time, we adopted in silico method to predict the 3D structure of GSAP via comparative modeling and studied the architecture and function of GSAP through simulation studies. Docking studies with 4153 phytochemicals revealed that GSAP having a better binding affinity with macaflavanone C, (E)-1-[2,4-dihydroxy-3-(3-methylbut-2-enyl)phenyl]-3-(2,2-dimethyl-8-hydroxy-2H-benzopyran-6-yl)prop-2-en-1-one, and monachosorin B as compared with the standard drug, imatinib. Further, the molecular dynamics analysis suggested that only two phytochemicals, namely, macaflavanone C and (E)-1-[2,4-dihydroxy-3-(3-methylbut-2-enyl)phenyl]-3-(2,2-dimethyl-8-hydroxy-2H-benzopyran-6-yl)prop-2-en-1-one) significantly disrupt the original property of GSAP and also cleared the absorption, distribution, metabolism, and excretion test. These natural compounds may be utilized in future for curing AD after further investigations.     

Involvement of active site in self-association of proteins: a case of alpha-chymotrypsin.

The self-association of proteolytic enzymes can be looked upon as an interesting possibility of the manifestation of enzyme-substrate complex. Hence the involvement of active site in such processes is a centre of investigation for many years. In the case of alpha-chymotrypsin, considerable controversy exists with regard to the involvement of active site of the enzyme in its self-association. A historical perspective of the problem and an overview of the available evidence, for and against, is presented and critically analysed. Despite contradicting observations, accumulated evidence indicates that His-57 and Ser-195 at the active site are involved, at least partially, in the self-association; a few other groups such as Tyr-146 and Met-192 are also involved in such processes.     

Glutathione and ascorbate reduction of the acetaminophen radical formed by peroxidase. Detection of the glutathione disulfide radical anion and the ascorbyl radical

The acetaminophen phenoxyl radical was generated by the oxidation of acetaminophen by horseradish peroxidase in a fast-flow ESR experiment, and its reaction with glutathione and ascorbate was studied. Glutathione reduces the phenoxyl radical of acetaminophen to regenerate acetaminophen and form the thiyl radical of glutathione. This thiyl radical reacts with the thiolate anion of glutathione to form the disulfide radical anion, which was detected and characterized by ESR spectroscopy. In the presence of ascorbate, the ascorbyl radical was produced by the reduction of the acetaminophen phenoxyl radical by ascorbate. This reaction results in the complete reduction of the free radical of acetaminophen, whereas the glutathione reduction of the phenoxyl radical of acetaminophen was not complete on the fast-flow ESR time scale of milliseconds. This suggests that ascorbate rather than glutathione is more likely to react with the acetaminophen phenoxyl free radical in vivo. In the presence of both ascorbate and higher concentrations of glutathione, the reaction with ascorbate is dominant. When cysteine was used in the place of reduced glutathione in the above assay system, the disulfide radical anion of cystine was observed in a manner similar to glutathione. These reactions may have significance in the detoxification of acetaminophen and the free radical metabolites of xenobiotics in general. Only in cells containing low levels of ascorbate can glutathione play a direct role in the detoxification of the acetaminophen phenoxyl radical.     

α-galactosidase from germinating guar (Cyamopsis tetragonolobus) seeds

The changes in α-galactosidase activity in guar (Cyamopsis tetragonolobus) seeds was followed during seven days of germination. The enzyme activity was maximal on the first day of germination and gradually decreased during subsequent days. On the second day of germination the partially purified enzyme upon ion-exchange chromatography on CM-Sephadex C-50 was resolved into α-galactosidase-A (anionic), α-galactosidase-C₁ (cationic) and α-galactosidase-C₂ (cationic) and their relative proportions were 28,12 and 60%, respectively. The combined α-galactosidase C₁ and C₂ activities increased in the first two days of germination followed by significant decrease after the 3rd day onwards, whereas α-galactosidase-A remained fairly constant throughout the germination period, α-Galactosidase-A and C2 had differentK _m and V_max values withp-nitrophenyl α-D-galactopyranoside, raffinose and melibiose as substrates and also differed in their thermal stabilities     

Novel enzymatic technique for recovery of starch from whole cassava chips without mechanical pulverization

Summary Different commercial enzymes, used individually or in combination, released upto 96% starch from whole cassava chips with pectinase I and cellulase combination. The enzymic action on macerating chips and disintegrating root cells was dependent on size of chips, presence of peel, temperature, time, agitation and type as well as concentration of enzymes. Significantly higher starch recovery and elimination of cost-intensive mechanical pulverization indicate potential of the enzymic technique.     

Induction of iron and cobalt dependent acrylonitrile hydratases inArthrobacter sp. IPCB-3

Summary ACN-hydratase inArthrobacter sp. IPCB-3 has been found to be induced by acetonitrile and urea and repressed by glucose. When acetonitrile was used as an inducer the synthesis of enzyme increased to about 2 folds and 4.5 folds on addition of iron and cobalt to the medium, respectively. However, when urea was used as an inducer only cobalt stimulated the enzyme synthesis and gave maximum activity (70 units/mg dry cells). In contrast to the stimulation of iron containing ACN-hydratase, yeast extract failed to stimulate further the synthesis of cobalt containing enzyme irrespective of the inducer present in the medium.     

Melanin-Mediated Synthesis of Silver Nanoparticles and Their Affinity Towards Tyrosinase

The bacterial strain Pseudomonas sp. SSA has capacity to produce extracellular melanin that sequesters heavy metals. The brown-black melanin pigment was observed in the culture liquid and mediated synthesis of silver nanoparticles (AgNPs). The AgNPs were characterized using UV–visible, dynamic light scattering, energy dispersive X-ray, Fourier transform infrared and surface plasmon resonance spectroscopy, scanning electron and transmission electron microscopy and selected area electron diffraction analysis. The synthesized nanoparticles were found to be spherical in shape with size in the range of 14–30 nm and showed high antimicrobial activity against pathogenic bacteria and fungi. These nanoparticles revealed binding affinity towards fungal and human tyrosinases with K_D 4.601 × 10^–10 and 2.816 × 10^–5 M, respectively. In addition, produced nanoparticles did not show any toxic effect towards HeLa cells up to 20 μg/mL. These nanoparticles could find application in medicine and cosmetics due to their enzyme inhibition and antimicrobial activities.     

Structural insights into suppressor of cytokine signaling 1 protein‐ identification of new leads for type 2 diabetes mellitus

The study considers the Suppressor of cytokine signaling 1 (SOCS1) protein as a novel Type 2 diabetes mellitus (T2DM) drug target. T2DM in human beings is also triggered by the over expression of SOCS proteins. The SOCS1 acts as a ubiquitin ligase (E3), degrades Insulin Receptor Substrate 1 and 2 (IRS1 and IRS2) proteins, and causes insulin resistance. Therefore, the structure of the SOCS1 protein was evaluated using homology‐modeling and molecular dynamics methods and validated using standard computational protocols. The Protein‐Protein docking study of SOCS1 with its natural substrates, IRS1 and IRS2, and subsequent solvent accessible surface area analysis gave insight into the binding region of the SOCS1 protein. The in silico active site prediction tools highlight the residues Val155 to Ile211 in SOCS1 being implicated in the ubiquitin mediated protein degradation of the proteins IRS1 and IRS2. Virtual screening in the active site region, using large structural databases, results in selective lead structures with 3‐Pyridinol, Xanthine, and Alanine moieties as Pharmacophore. The virtual screening study shows that the residues Glu149, Gly187, Arg188, Leu191, and Ser205 of the SOCS1 are important for binding. The docking study with current anti‐diabetic therapeutics shows that the drugs Glibenclamide and Glyclopyramide have a partial affinity towards SOCS1. The predicted ADMET and IC₅₀ properties for the identified ligands are within the acceptable range with drug‐like properties. The structural data of SOCS1, its active site, and the identified lead structures are expedient in the development of new T2DM therapeutics.