Stereoselective synthesis of jaspine B from D-xylose

The natural cytotoxic marine compound, jaspine B, is stereoselectively synthesized from D-xylose in 11 linear steps with a 23.9% overall yield. The key step in the synthesis involves an iodine-induced debenzylation of a primary alcohol and the subsequent 2,5-cyclization to fit the required configuration of jaspine B. A preliminary bioassay shows strong inhibition activities against human MDA231, Hela, and CNE cell lines, indicating potential usage in various cancer treatments.     

A Novel Jaspine BCeramide Hybrid Modulates Sphingolipid Metabolism

A new sphingolipid hybrid molecule was designed to assemble, within a tail‐to‐tail double‐chain structure, the ceramide hydrophilic moiety and the tetrahydrofuran pharmacophore of jaspine B, a natural product known to interfere with sphingolipid metabolism. This compound was prepared through acylation of sphingosine with a jaspine B derivative bearing a COOH group in the terminal position of the aliphatic backbone. This new hybrid molecule was evaluated for its capacities to affect melanoma cell viability and sphingolipid metabolism. While retaining the cytotoxicity of ceramide itself, this compound was shown to lower the sphingomyelin cellular levels and significantly enhance the production of sphingosine‐1‐phosphate, thus representing a novel sphingolipid metabolism modulator.     

Pachastrissamine (jaspine B) and its stereoisomers inhibit sphingosine kinases and atypical protein kinase C

Sphingosine kinases (SphKs) are oncogenic enzymes that regulate the critical balance between ceramide and sphingosine-1-phosphate. Much effort has been dedicated to develop inhibitors against these enzymes. Naturally occurring pachastrissamine (jaspine B) and all its stereoisomers were prepared and evaluated for their inhibitory effects against SphKs. All eight stereoisomers exhibited moderate to potent inhibitory activity against SphK1 and SphK2. Inhibitory effects were profiled against protein kinase C (PKC) isoforms by in vitro experiments. Atypical PKCs (PKCζ and PKCι) were inhibited by several pachastrissamine stereoisomers. The improved activity over N,N-dimethylsphingosine suggests that the cyclic scaffold in pachastrissamines facilitates potential favorable interactions with SphKs and PKCs.     

Lipophosphonoglycan of the plasma membrane of A canthamoeba castellanii. Inositol and phytosphingosine content and general structural features.

Lipophosphonoglycan, a major component of the plasma membrane of Acanthamoeba castellanii, has now been shown to contain 8% inositol and 13% C25- and C24-phytosphingosines in addition to the previously identified content of neutral sugars (26%), amino sugars (3%), aminophosphonates (10%), acidhydrolyzable phosphate (3%), and long chain fatty acids (14%). The fatty acids and phytosphingosines are in ceramide groups. Lipophosphonoglycan can be separated by dodecyl sulfate-polyacrylamide electrophoresis into two major components that are similar in composition except for different oligosaccharide groups. A tentative structural model incorporating these features is proposed in which each of the two components of lipophosphonoglycan is conceived as an oligomeric inositol-containing glycosphingolipid.     

High-performance liquid chromatography analysis of molecular species of sphingolipid-related long chain bases and long chain base phosphates in Saccharomyces cerevisiae after derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate.

The molecular species of dihydrosphingosines and phytosphingosines and their 1-phosphates with carbon chain lengths from 16 to 20 have been tagged with the fluorescent amino group reagent, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. All these derivatives could be resolved by reversed phase HPLC on a C18 column. A convenient one-pot method is described whereby lipid extracts from strains of Saccharomyces cerevisiae containing carbon chain length homologs of sphingolipid long chain bases and their phosphorylated derivatives were directly reacted with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate, ester lipids were deacylated, and the reaction mixtures were subjected to liquid chromatography. Five molecular species of both sphingolipid long chain bases and their phosphorylated derivatives are for the first time separated and analyzed. The procedure is quite sensitive, requiring only approximately 10(8) wild-type cells.     

Discovery of novel jaspine B analogues as autophagy inducer

A series of 2-alkylaminomethyl jaspine B analogues were synthesized and evaluated for their cytotoxic effects on human lung adenocarcinoma, breast cancer, and prostate cancer cell lines and a mouse melanoma cell line. Most of the compounds exhibited moderate to good activity against the cancer cell lines. Compound 7f showed the best overall cytotoxicity on PC-3 cells (IC₅₀?=?0.85?μM). Further mechanistic studies revealed that compound 7f induced marked changes in PC-3 cell morphology, disrupted the mitochondrial membrane potential, and increased expression of the autophagy proteins beclin-1, LC3, and P62.     

Ceramide composition of the psoriatic scale

This paper investigates the ceramide composition of the psoriatic scale compared with that of normal human SC. A method was optimalized, based on TLC separation followed by densitometry, allowing the provision of good resolution and quantification of ceramide fractions from both normal and pathological specimens. Seven ceramide fractions were isolated and submitted to compositional analysis. The obtained results suggested a revisitation of previous ceramide designation. Therefore a simple classification is suggested, based on grouping ceramides carrying structural similarities under common codes. According to these rules, ceramides were grouped into five classes designated as: (1) Cer[EOS], which contains ester-linked fatty acids, ω-OH fatty acids and sphingosines; (2) Cer[NS], which contains non-OH fatty acids and sphingosines; (3) Cer[NP], which contains non-OH fatty acids and phytosphingosines; (4) Cer[AS], which contains α-OH fatty acids and sphingosines; (5) Cer[AP], which contains α-OH fatty acids and phytosphingosines. Analysis of ceramides from the psoriatic scale, compared to those from normal human SC, resulted in an impairment of the Cer[EOS] content as well as of the ceramides containing phytosphingosine, with concurrent increase in ceramides containing sphingosine, being the total amount maintained identical. Since one of the suggested pathways for phytosphingosine biosynthesis involves the water addition to the corresponding sphingosine double bond, we can speculate that the observed alterarion is due to a deranged water bioavailability, associated with psoriaris.     

Gangliosides from the eggs of the sea urchin, Anthocidaris crassispina

NeuGc alpha 2-6Glc beta 1-1Cer (M5 ganglioside) and HSO3-8NeuGc alpha 2-6Glc beta 1-1Cer (T1 ganglioside) were purified by column chromatographies with DEAE-Sephadex A-25 and silicic acid from the eggs of the sea urchin, Anthocidaris crassispina. Their chemical structures were determined by gas-liquid chromatography, methylation analysis, enzymatic hydrolysis, negative-ion fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance spectroscopy. Long-chain base compositions of both gangliosides were almost identical: all the long-chain bases were phytosphingosines, and C18-phytosphingosine accounted for more than 95% of them. Fatty acid compositions were also very similar: the main fatty acids were 22:1, 23:1, 24:1, and their 2-hydroxylated forms, and the 2-hydroxy fatty acids amounted to 65.3 and 74.3% of the fatty acids in M5 and T1 gangliosides, respectively. Proton nuclear magnetic resonance spectroscopic study revealed a downfield-shifted H8 proton signal of NeuGc residue in T1 ganglioside, in agreement with the presence of sulfate ester at the C8 position.     

Studies on the glycosphingolipids of the starfish, Asterina pectinifera. II. Isolation and characterization of a novel ganglioside with an internal sialic acid residue.

1. Three gangliosides, provisionally named Gangliosides 1, 2, and 3, were obtained from the lipid extract of the starfish, Asterina pectinifera by silicic acid, DEAE-Sephadex, and Iatrobeads column chromatography. The most abundant, Ganglioside 3 (37.7 microgram/g wet weight of starfish) was isolated in the pure state and its chemical structure was studied. 2. The sugar composition of Ganglioside 3 consisted of arabinose, glucose, galactose, and sialic acid (as N-glycolylneuraminic acid) in a molar ratio of 1:1:3:1. Three sialic acid-containing oligosaccharide fragments were isolated from partial acid hydrolysates of the ganglioside by Dowex 1 X 8 (acetate form) column chromatography and preparative paper chromatography, and identified as Gal leads to NeuGc, Gal (1 leads to 4)[Gal(1 leads to 8)]NeuGc and Ara-(1 leads to 6)Gal(1 leads to 4)[Gal(1 leads to 8)]NeuGc. 3. The structure of Ganglioside 3 was postulated to be: Araf,p(1 leads to 6)Galpbeta(1 leads to 4)[Galpbeta(1 leads to 8)]NeuGc(2 leads to 3)Galpbeta(1 leads to 4)Glcpbeta(1 leads to 1)-ceramide. This is a unique structure with the sialic acid residue internally located in the sugar chain. 4. The ganglioside contained saturated 2-hydroxy fatty acids ranging in length from C16 to C24, among which C22, C23, and C24 acids were predominant. The long-chain bases consisted exclusively of C16, C17, and C18 phytosphingosines of iso and anteiso types.     

Gas-chromatography/mass-spectrometry analysis of human skin constituents as heptafluorobutyrate derivatives with special reference to long-chain bases

The composition of the constituents (monosaccharides, long-chain bases, and fatty acids) found in an ethanol extract of the human skin could be determined, without time-consuming steps of purification, after acid-catalyzed anhydrous methanolysis, followed by the formation of volatile derivatives with heptafluorobutyric anhydride and gas-chromatography/mass-spectrometry analysis. Despite the extreme heterogeneity of such extracts, the electron impact analysis of the constituents allowed qualitative and quantitative determinations of monosaccharides, long-chain bases, fatty acids, and alkyl-glycerols. Throughout the different long-chain bases, sphingenines (Sphes), sphinganines, phytosphingosines, and 6-hydroxy-Sphes (6oh-Sphes) can be identified and quantified. Long-chain bases with a chain-length up to 28 carbon atoms can be identified through specific fragmentation patterns in the electron impact mode. Particular attention was drawn to the behavior of compounds of the family of 6oh-Sphes upon acid-catalyzed methanolysis.     

Lipids of higher fungi. II. The nature of cerebrins and cerebrosides from the mushroom Clitocybe tabescens Scop

Four cerebrins (ceramides) and two cerebrosides were isolated from the mushroom Clitocybe tabescens by combining column chromatography and preparative thin-layer chromatography. Quantification of the amide-linked nonhydroxy and hydroxy fatty acids (NFA and HFA) was obtained by gas—liquid chromatography. The nature of the long-chain bases was determined by thin-layer chromatography. The major acids in cerebrins were: NFA 16:0, 17:0, 18:X, 22:0 and HFA h16:0, h18:0, h22:0, h24:0. In cerebrosides predominated 17:0, 22:0 and h16:0. The component long-chain bases in all samples were sphingosines, dihydrosphingosines, phytosphingosines and unidentified more polar bases. Glucose was detected as the sole sugar constituent in cerebrosides.     

Single-step gas chromatography-mass spectrometry analysis of glycolipid constituents as heptafluorobutyrate derivatives with a special reference to the lipid portion

In a previous work (Zanetta et al. Glycobiology 9, 255-266 (1999)), it was reported that all constituents of gangliosides could be obtained as heptafluorobutyrate derivatives after methanolysis in a single gas chromatography analysis. This report demonstrates that gas chromatography coupled with mass spectrometry in the electron impact mode allows identification and quantification of long-chain bases and fatty acids without interference from monosaccharides. On the basis of ions specific for families and for individual compounds, sphingosines, sphinganines, and phytosphingosines (including ramified, unsaturated, hydroxylated, and etherified compounds) can be identified. Fatty acid methyl esters, including linear, ramified, unsaturated, and hydroxylated species, are identified and quantified in the same way. Possible extensions of this method to the fatty moiety of other lipids (alkylacylglycerol and dimethyl acetal) are discussed.     

Production of tetraacetyl phytosphingosine (TAPS) in Wickerhamomyces ciferrii is catalyzed by acetyltransferases Sli1p and Atf2p

Wickerhamomyces ciferrii secretes tetraacetyl phytosphingosine (TAPS), and in this study, the catalyzing acetyltransferases were identified using mass spectrometry-based proteomics. The proteome of wild-type strain NRRL Y-1031 served as control and was compared to the tetraacetyl phytosphingosine defective mating type NRRL Y-1031-27. Acetylation of phytosphingosine in W. ciferrii is catalyzed by acetyltransferases Sli1p and Atf2p, encoded by genes similar to Saccharomyces cerevisiae YGR212W and YGR177C, respectively. Ablation of SLI1 resulted in an almost complete loss of tri- and tetraacetyl phytosphingosines, whereas the loss ATF2 resulted in an 15-fold increase in triacetyl phytosphingosine. Most likely, it is the concerted action of these two acetyltransferases that yields tetraacetyl phytosphingosine, in which Sli1p catalyzes initial O- and N-acetylation, producing triacetyl phytosphingosine. Finally, Atf2p catalyzes final O-acetylation to yield tetraacetyl phytosphingosine. The current study demonstrates that mass spectrometry-based proteomics can be employed to identify key steps in ill-explored metabolite biosynthesis pathways of nonconventional microorganisms. Furthermore, the identification of phytosphingosine as substrate for alcohol acetyltransferase Atf2p broadens the known substrate range of this enzyme. This interesting property of Atf2p may be exploited to enhance the secretion of heterologous compounds.     

Gangliosides of the starfish Aphelasterias japonica, evidence for a new linkage between two N-glycolylneuraminic acid residues through the hydroxy group of the glycolic acid residue

Mono- and disialogangliosides containing glucose, galactose and sialic acids were isolated from the total lipid extract of hepatopancreas of the starfish Aphelasterias japonica. Their structures were elucidated by total and partial acid hydrolysis, trideuteriomethylation analysis, neuraminidase treatment, chromium trioxide oxidation, methanolysis and periodate oxidation. The monosialoganglioside was identified as 8-O-methyl-N-glycolylneuraminosyl-alpha-(2-3)-galactosyl-beta-(1- 4)-glucosyl-beta-(1-1)-ceramide. The disialoganglioside has the additional N-glycolylneuraminic acid or its 8-O-methyl derivative residue at the subterminal position to which the terminal sialic acid residue is linked through the hydroxy group of the glycolic acid unit. The long-chain bases were found to be mixtures of phytosphingosines with both branched and linear chains, and the fatty acids were shown to be mixtures of normal and alpha-hydroxy fatty acids, the latter amounted to about 90% of the fatty-acid mixtures. The composition of the lipid moieties of the gangliosides was determined by GLC and GLC-MS.     

A novel difucosylated neutral glycosphingolipid from the eggs of the sea urchin, Hemicentrotus pulcherrimus: I. Purification and structural determination of the glycolipid.

A novel fucose-containing neutral glycosphingolipid (GL-5) was purified from the eggs of the sea urchin, Hemicentrotus pulcherrimus. The chemical structure was determined to be Fuc alpha 1-3GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-4Glc beta 1-1Cer by methylation analysis, partial acid hydrolysis, fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance spectroscopy. The unique characteristics of GL-5 are that: the reducing terminal disaccharide portion is not Gal beta 1-4Glc but GlcNAc beta 1-4Glc; it includes a GalNAc beta 1-4GlcNAc sequence and a Fuc-GalNAc linkage; the defucosylated core is a novel trisaccharide chain; and the sugar structure is one of the smallest ever characterized for a difucosylated glycolipid. The major fatty acids were 22:1 and 22h:1, and about 30% of the total acids was 2-hydroxylated. All the long-chain bases were phytosphingosines, of which about 90% was n-t18:0. The similarity of the ceramide moiety to that of glucosylceramide from the same eggs [Kubo, H. et al. (1992) J. Biochem. 111, 726-731] suggests a close biosynthetic relationship between GL-5 and the glucosylceramide.     

Covalent binding properties of the human complement protein C4 and hydrolysis rate of the internal thioester upon activation.

The complement proteins C3 and C4 have an internal thioester. Upon activation on the surface of a target cell, the thioester becomes exposed and reactive to surface-bound amino and hydroxyl groups, thus allowing covalent deposition of C3 and C4 on these targets. The two human C4 isotypes, C4A and C4B, which differ by only four amino acids, have different binding specificities. C4A binds more efficiently than C4B to amino groups, and C4B is more effective than C4A in binding to hydroxyl groups. By site-directed mutagenesis, the four residues in a cDNA clone of C4B were modified. The variants were expressed and their binding properties studied. Variants with a histidine residue at position 1106 showed C4B-like binding properties, and those with aspartic acid, alanine, or asparagine at the same position were C4A-like. These results suggest that the histidine is important in catalyzing the reaction of the thioester with water and other hydroxyl group-containing compounds. When substituted with other amino acids, this reaction is not catalyzed and the thioester becomes apparently more reactive with amino groups. This interpretation also predicts that the stability of the thioester in C4A and C4B, upon activation, will be different. We measured the time course of activation and binding of glycine to C4A and C4B. The lag in the binding curve behind the activation curve for C4A is significantly greater than that for C4B. The hydrolysis rates (k0) of the thioester in the activated proteins were estimated to be 0.068 s-1 (t1/2 of 10.3 s) for C4A and 1.08 s-1 (t1/2 of 0.64 s) for C4B. These results indicate that the difference in hydrolysis rate of the thioester accounts, at least in part, for the difference in the binding properties of C4A and C4B.     

Oxygen binding and aggregation of bullfrog hemoglobin

The hemoglobin of the bullfrog, Rana catesbeiana, forms aggregates larger than tetramers in two ways. The first, which results from intermolecular disulfide bonds, can be prevented by treatment with iodoacetamide. The second way results from the association of the deoxygenated forms of the two major components, B and C, to form reversibly an aggregate which is believed to be a trimer, BC2. The sedimentation velocity data show that the stoichiometry of the aggregate cannot be 1:1. The electrophoretic pattern of the deoxygenated B/C mixture suggests that the association is not indefinite. No significant aggregation of the separate deoxygenated tetramers of the components nor of the oxygenated components or mixture occurs. Gel chromatography of the oxygenated forms of components B and C and of mixtures indicates that the B and C tetramers both form dimers upon dilution with a dissociation constant of 2-3 micron. The oxygen-binding data indicate that the B/C aggregate has a much lower oxygen affinity than its constituent tetramers. Dissociation of the low affinity B/C aggregate to higher affinity B and C tetramers with increasing oxygenation gives rise to enhanced cooperativity as measured by the Hill coefficient which is maximal near 75-80% oxygenation and is as high as 4.1 at a heme concentration of 15 mM.     

乙肝患者病变程度与病毒基因分型的相关性分析

目的探讨乙型肝炎（乙肝）病毒（HBV）基因分型与病变程度之间的关系。方法对165例经肝组织切片证实的急性轻型肝炎、轻度慢性肝炎（CHB）、中度慢性肝炎和重度慢性肝炎及肝硬化的乙肝患者血清进行基因分型。结果基因型以B型和C型为主,分别为12．1％和86．7％。C型中度慢性肝炎所占的百分比显著高于B型,而重度慢性肝炎在B型和C型中所占百分比差异无统计学意义;基因C型感染者HBeAg阳性率显著高于基因B型感染者,而基因C型感染者中HBeAb阳性率显著低于基因B型感染者。结论C型HBV感染和乙肝病情加重有一定关系,而B型HBV感染者预后相对较好。     

Arabidopsis CYP90B1 catalyses the early C-22 hydroxylation of C27, C28 and C29 sterols

Arabidopsis dwf4 is a brassinosteroid (BR)-deficient mutant, and the DWF4 gene encodes a cytochrome P450, CYP90B1. We report the catalytic activity and substrate specificity of CYP90B1. Recombinant CYP90B1 was produced in Escherichia coli, and CYP90B1 activity was measured in an in vitro assay reconstituted with NADPH-cytochrome P450 reductase. CYP90B1 converted campestanol (CN) to 6-deoxocathasterone, confirming that CYP90B1 is a steroid C-22 hydroxylase. The substrate specificity of CYP90B1 indicated that sterols with a double bond at positions C-5 and C-6 are preferred substrates compared with stanols, which have no double bond at the position. In particular, the catalytic efficiency (k(cat)/K(m)) of CYP90B1 for campesterol (CR) was 325 times greater than that for CN. As CR is more abundant than CN in planta, the results suggest that C-22 hydroxylation of CR before C-5alpha reduction is the main route of BR biosynthetic pathway, which contrasts with the generally accepted route via CN. In addition, CYP90B1 showed C-22 hydroxylation activity toward various C(27-29) sterols. Cholesterol (C27 sterol) is the best substrate, followed by CR (C28 sterol), whereas sitosterol (C29 sterol) is a poor substrate, suggesting that the substrate preference of CYP90B1 may explain the discrepancy between the in planta abundance of C27/C28/C29 sterols and C27/C28/C29 BRs.