Search

Signal peptide peptidase (SPP) is an atypical aspartic protease that hydrolyzes peptide bonds within the transmembrane domain of substrates and is implicated in several biological and pathological functions. Here, we analyzed the structure of human SPP by electron microscopy and reconstructed the three-dimensional structure at a resolution of 22 Å. Enzymatically active SPP forms a slender, bullet-shaped homotetramer with dimensions of 85 × 85 × 130 Å. The SPP complex has four concaves on the rhombus-like sides, connected to a large chamber inside the molecule. Intriguingly, the N-terminal region of SPP is sufficient for the tetrameric assembly. Moreover, overexpression of the N-terminal region inhibited the formation of the endogenous SPP tetramer and the proteolytic activity within cells. These data suggest that the homotetramer is the functional unit of SPP and that its N-terminal region, which works as the structural scaffold, has a novel modulatory function for the intramembrane-cleaving activity of SPP. [ABSTRACT FROM AUTHOR]

Abstract: Natural steroidal glycosides containing α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranose (chacotriose) at the oligosaccharide moiety exhibit anti-cancer and anti-herpes activities. To investigate the structure–activity relationships of the aglycone parts of chacotriosides, we developed a synthesis method for chacotriosyl glycosides having various aglycones. In the process, it was revealed that α-chacotriosyl glycosides could be obtained mainly by using a trichloroacetimidate donor, while β-chacotriosyl glycosides were afforded by using phosphite and phosphate donors. In cytotoxicity tests using the A549 and HepG2 cell lines, naturally occurring β-chacotriosyl diosgenin and cholestanol exhibited higher activities than the corresponding α-chacotriosyl glycosides. [Copyright &y& Elsevier]

In many languages there are words that behave like lexical verbs and on the one hand and like functional categories expressing distinctions of tense, aspect, modality, etc. on the other. The grammatical status of such words is frequently controversial; while some authors treat them as belonging to one and the same grammatical category, others assign them to different categories. The present paper is concerned with such a case of “doublets”: Looking in more detail at the German item drohen ‘to threaten’, it attempts to offer an account of the differences in the lexical and functional structure of this item by using grammaticalization theory as a framework. As the data presented in the paper suggest, this model in fact accounts for most though not for all of the properties characterizing the structure of the item. It is argued that in addition to synchronic analysis, a diachronic and comparative perspective is required in order to arrive at a more comprehensive understanding of the interface between lexical and functional structures. [Copyright &y& Elsevier]

Abstract: α-l-Rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranose (chacotriose) is the oligosaccharide moiety of dioscin. Chacotriosyl trichloroacetimidate was synthesized from d-glucose and l-rhamnose, and glycosylated to mevalonate (diosgenin, cholesterol, and glycyrrhetic acid) to yield dioscin and neosaponins. In order to simplify the structure of the aglycone part, the mevalonate moiety was replaced with double-chain neoglycolipids that mimicked glycosyl ceramides. A cytotoxicity test revealed the importance of the glycosidic linkage of the naturally occurring β-form and that dioscin and the neoglycolipid with the longest chain showed a moderate activity. [Copyright &y& Elsevier]

Abstract: Calpain-mediated proteolysis has been implicated as a major process in neuronal cell death including retinal neurological degeneration. The previously reported calpain inhibitor SJA6017 (1) showed oral efficacy in a retinal pharmacological model, but its oral bioavailability was low due to the metabolic lability and low water-solubility. The purpose of present study was to identify good orally bioavailable calpain inhibitors. A series of water-soluble dipeptidyl α-ketoamides containing a pyridine moiety at P3 were designed, synthesized, and evaluated for their oral bioavailability and retinal penetration. Introduction of a pyridineethanol moiety provided the potent α-ketoamide inhibitor 8 with good oral bioavailability. Compound 8 showed about 12-fold higher retinal AUC than 1. [Copyright &y& Elsevier]

Abstract: A novel series of dipeptidyl α-ketoamide derivatives with amphiphile was designed and synthesized as water-soluble calpain inhibitors. The introduction of amphiphiles at the P3 site increased water solubility without loss of membrane permeability and provided the oral available inhibitors. Extension of the ethylene glycol chain at the P3 site led to an improvement in persistence of plasma levels. In particular, introduction of a combination of a diethylene glycol methyl ether moiety at the P3 site, a phenylalanine residue at the P1 site and a cyclopropyl moiety at the P′ site was the most effective modification for an increase in plasma drug exposure. [Copyright &y& Elsevier]

A novel series of dipeptidyl α-ketoamide derivatives with amphiphile was designed and synthesized as water-soluble calpain inhibitors. The introduction of amphiphiles at the P3 site increased water solubility without loss of membrane permeability and provided the oral available inhibitors. Extension of the ethylene glycol chain at the P3 site led to an improvement in persistence of plasma levels. In particular, introduction of a combination of a diethylene glycol methyl ether moiety at the P3 site, a phenylalanine residue at the P1 site and a cyclopropyl moiety at the P′ site was the most effective modification for an increase in plasma drug exposure. [ABSTRACT FROM AUTHOR]

A novel series of 6-hydroxy-3-morpholinones, in which the functional aldehyde and the hydroxy group of P2 site form a cyclic hemiacetal, was identified as calpain inhibitors. The placement of isobutyl group at the 2-position of the 3-morpholinone was the most effective modification for inhibiting μ- and m-calpains. Substitutions of benzyl at the 5-position in the S-configuration had virtually no effect on inhibitory activity. Several compounds showed appreciable selectivity for calpains over cathepsin B. NMR experiments demonstrated that the representative 6-hydroxy-3-morpholinone 10a (SNJ-1757) was more stable to nucleophilic attack than the corresponding aldehyde inhibitor 24. Furthermore, 6-hydroxy-3-morpholinone 10a proved to have better corneal permeability than aldehyde inhibitor 24 in an in vitro experiment. [Copyright &y& Elsevier]

γ-Secretase is an atypical aspartyl protease that cleaves amyloid β-precursor protein to generate Aβ peptides that are causative for Alzheimer disease. γ-Secretase is a multimeric membrane protein complex composed of presenilin (PS), nicastrin, Aph-1, and Pen-2. Pen-2 directly binds to transmembrane domain 4 of PS and confers proteolytic activity on γ-secretase, although the mechanism of activation and its role in catalysis remain unknown. Here we show that an addition of amino acid residues to the N terminus of Pen-2 specifically increases the generation of Aβ42, the longer and more aggregable species of Aγ. The effect of the N-terminal elongation of Pen-2 on Aγ42 generation was independent of the amino acid sequences, the expression system and the presenilin species. In vitro γ-secretase assay revealed that Pen-2 directly affects the Aβ42-generating activity of γ-secretase, The elongation of Pen-2 N terminus caused a reduction in the water accessibility of the luminal side of the catalytic pore of PS1 in a similar manner to that caused by an Aγ42-raising γ-secretase modulator, fenofibrate, as determined by substituted cysteine accessibility method. These data suggest a unique mechanism of Aβ42 overproduction associated with structural changes in the catalytic pore of presenilins caused commonly by the N-terminal elongation of Pen-2 and fenofibrate. [ABSTRACT FROM AUTHOR]

Resin glycosides act as laxatives in crude drugs derived from plants of the Convolvulaceae family. These compounds have exhibited antibacterial, ionophoric, anti-inflammatory, antiviral, and multidrug resistance-modulating properties, as well as cytotoxicity against cancer cells. This study investigated the organic acid, hydroxyl fatty acid, monosaccharide, and glycosidic acid components of the crude resin glycoside fraction obtained from the methanol extract of Ipomoea alba L. (Convolvulaceae) seeds, which was subjected to alkaline and acidic hydrolysis. The alkaline hydrolysis yielded acetic, isobutyric, (E)-2-methylbut-2-enoic, and 2 S -methyl-3 S -hydroxybutyric acids as organic acid components, along with a glycosidic acid fraction. The acidic hydrolysis of the glycosidic acid fraction resulted in the isolation of 11 S -hydroxytetradecanoic and 11 S -hydroxyhexadecanoic acids as hydroxyl fatty acid components, as well as d -glucose, d -quinovose, d -fucose, d -xylose, and l -rhamnose as monosaccharide components. In addition, 10 new glycosidic acid methyl esters were isolated from the glycosidic acid fraction treated with trimethylsilyldiazomethane–hexane, along with one known glycosidic acid methyl ester. Of these, eight compounds contained new glycans. Four of these compounds were unusual natural glycosides with four glycosidic linkages to one monosaccharide. Their structures were determined using MS and NMR spectral analyses, which provided valuable insights into the unique glycosidic composition of I. alba seeds. [Display omitted] • The components of the resin glycoside fraction of Ipomoea alba were studied. • Ten new glycosidic acids were isolated as methyl esters. • Of the glycosidic acid methyl esters isolated, eight contained new glycans. • Four methyl esters had four glycosidic linkages to one monosaccharide. [ABSTRACT FROM AUTHOR]

Resin glycosides are commonly found in plants belonging to the Convolvulaceae family. Ipomoea lacunosa L. (Convolvulaceae) is an herbaceous vine native to the United States. The resin glycosides of this plant have not been studied in detail. In this study, the components of the crude resin glycoside fraction extracted from the seeds of I. lacunosa are characterized. Alkaline hydrolysis of the crude resin glycoside fraction obtained from methanolic extract of the seeds yielded three organic acids, namely, 2 S -methylbutyric, (E)-2-methylbut-2-enoic, and 2 R -methyl-3 R -hydroxybutyric acids, and a glycosidic acid fraction. Acidic hydrolysis of the glycosidic acid fraction yielded hydroxyl fatty acid components, including 7 S -hydroxydecanoic, 11 S -hydroxytetradecanoic, 11 S -hydroxyhexadecanoic, 3 S ,11 S -dihydroxytetradecanoic, 3 S ,11 S -dihydroxyhexadecanoic, and 3 S ,12 S -dihydroxyhexadecanoic acids, as well as monosaccharide components, including d -glucose, d -quinovose, d -fucose, and l -rhamnose. Trimethylsilyldiazomethane–hexane treatment of the glycosidic acid fraction further yielded eleven previously undescribed glycosidic acid methyl esters and two known glycosidic acid methyl esters. The structures of the obtained compounds were characterized using various spectral techniques. Four of the undescribed compounds were hexaglycosides, five were heptaglycosides, and two were octaglycosides. The aglycone of these compounds was either methyl 11 S -hydroxytetradecanoate, methyl 3 S ,11 S -dihydroxytetradecanoate, or methyl 3 S ,11 S -dihydroxyhexadecanoate. Among the undescribed compounds identified, eight contained novel glycans, and three were rare bisdesmosides with sugar linkages at the C-3 and C-11 positions of methyl 3 S ,11 S -dihydroxytetradecanoate. [Display omitted] • Thirteen glycosidic acid components of I. lacunosa were isolated as methyl esters. • Of the glycosidic acid methyl esters isolated, eleven were undescribed compounds. • Eight glycosidic acid methyl esters contained undescribed glycans. • Two of the undescribed glycosidic acid methyl esters were octaglycosides. • Three glycosidic acid methyl esters were rare bisdesmosides. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to verify the antitumor role of the β-d-glucopyranosyl-(1→2)-O-[β-d-xylopyranosyl-(1→3)]-O-β-d-glucopyranosyl-(1→4)-d-galactopyranosyl (lycotetraosyl) moiety present in steroidal glycosides from Solanaceous plants. We explored a new chemical trans-glycosylation method using an endoglycosidase called tomatinase that is produced by the tomato pathogen, Fusarium oxysporum f. sp. lycopersici. The lycotetraose, which was prepared by enzymatic hydrolysis of α-tomatine with tomatinase, was converted to glycosyl donors such as trichloroacetimidate, fluoride, and thioglycoside. All obtained glycosyl donors were glycosylated with cholesterol to form α-lycotetraosyl cholesterols in a stereoselective manner. The obtained lycotetraosyl derivatives together with typical natural lycotetraosyl glycosides were examined for their antiproliferative activity. [Copyright &y& Elsevier]

Abstract: A reductive coupling reaction was effectively developed to convert an aldehyde to its symmetrical ether. The successful reactions required Et3SiH and CH2Cl2 as the suitable solvent in the presence of a catalytic amount of In(OTf)3. Various aldehydes were subjected to the method, and each afforded the expected ethers in good to excellent yields. [Copyright &y& Elsevier]