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Makoto Ubukata

Publications and source records attributed to Makoto Ubukata.

18 recordsLinked to original sources
PubMed2006

Chemical synthesis of beta-O-4 type artificial lignin.

An artificial lignin polymer containing only the beta-O-4 substructure was synthesized. The procedure consists of two key steps: 1) polycondensation of a brominated monomer by aromatic Williamson reaction; and 2) subsequent reduction of the carbonyl polymer. 13C-NMR and HMQC spectra of the polymer were consistent with beta-O-4 substructures in milled wood lignin isolated from Japanese fir wood. The weight average degree of polymerization (DP(w)) ranged from 19.5 to 30.6, which is comparable to enzymatically synthesized artificial lignin from p-hydroxycinnamyl alcohols (dehydrogenation polymer, DHP) and some isolated lignins. Using this new lignin model polymer, it will now be possible to reinvestigate the properties and reactivity of the main lignin structure in terms of its polymeric character.

Acetylation↗
PubMed2005

Easy synthesis of beta-O-4 type lignin related polymers.

The beta-O-4 structure is the most abundant substructure in lignin. Lignin related polymers composed of only the beta-O-4 structure were prepared using simple aromatic compounds as starting materials. Acetophenone derivatives were brominated, polymerized in the presence of K2CO3 and reduced with NaBH4 to give the lignin related polymers. These are linear polymers which resemble natural lignins in their structures, although they do not have a gamma-hydroxymethyl group. The number average degree of polymerization (DPn) was determined with peracetate of the polymers by gel permeation chromatography. The DPn of guaiacyl type polymers ranged from 15.2-21.4, where the value for the syringyl type was 11.3 and for the p-hydroxyphenyl type 16.9. The Guaiacyl type polymer was very soluble in usual lignin solvents such as 1, 4-dioxane-water (96 : 4, v/v) and DMSO, but only slightly soluble in acetone-water (9 : 1, v/v).

Acetylation↗
PubMed2005

Protein phosphatase type 2A, PP2A, is involved in degradation of gp130.

The interleukin-6 (IL-6) stimulates growth in cells such as multiple myeloma and B-cell plasmacytomas/hybridomas, while it inhibits growth in several myeloid leukemia cells. The IL-6 receptor has subunit called gp130. It was reported that Ser-782 of gp130 is phosphorylated by unidentified kinase(s) in cell extracts, and level of gp130 (S782A) transiently expressed on the cell surface of COS-7 is 6-times higher than that of the wild type. These results motivated us to analyze whether the phosphorylation of gp130 at Ser-782 is involved in its degradation or not. In this study, we demonstrated here that treatment of HepG2 cells with okadaic acid (OA), a potent inhibitor for PP2A, promotes phosphorylation of gp 130 at Ser-782 and degradation of gp 130. MG115, a proteasome inhibitor, suppressed this degradation. These effects of OA could not be replaced with tautomycetin (TC), an inhibitor for PP1. Purified PP2A dephosphorylated phospho-Ser-782 of gp130 in vitro. IL-6-induced activation of Stat3 was suppressed by preincubation of the cells with OA, suggesting that the IL-6 signaling pathway was blocked by OA through degradation of gp 130. Taken together, present results strongly suggest that degradation of gp 130 is regulated through a phosphorylation-dephosphorylation mechanism in which PP2A is crucially involved and that gp 130 is a potential therapeutic target in cancers.

Antigens, CD↗
PubMed2005

Biosynthesis of indocarbazostatin B, incorporation of D-[U-13C] glucose and L-[2-13C] tryptophan.

High incorporation of D-[U-13C] glucose and L-[indole-2-13C] tryptophan into indocarbazostatin B (2) was observed in a biosynthetic study using a mutant strain, Streptomyces sp. MUV-7-8. The original strain, Streptomyces sp. TA-0403 produced a small amount of indocarbazostatin (1) and indocarbazostatin B (2), which displayed potent biological activities. To facilitate biosynthetic studies, we selected high indocarbazostatin producing mutant strains. The first mutants, Streptomyces sp. MUV-6-83 and MUV-6-17, produced indocarbazostatins C (3) and D (4) as well as 1 and 2. When the production medium was supplemented with D-tryptophan, the MUV-6-17 mutant produced K252c (5), whereas when L-tryptophan was added, it produced K252d (6). On further UV treatment of the mutant strain MUV-6-83, we finally obtained a new mutant producer, Streptomyces sp. MUV-7-8, that produced 2 as a major metabolite with higher productivity. This mutant producer enabled us to do a feeding experiment of the envisioned precursors, glucose and tryptophan.

Anti-Bacterial Agents↗
PubMed2005

Inhibition of preadipocyte differentiation by germacranolides from Calea urticifolia in 3T3-L1 cells.

The effects of germacranolides isolated from Calea urticifolia on adipocytic differentiation of 3T3-L1 cells were examined. These germacranolides inhibited adipogenesis at a concentration of 1.25-5 microM. But no inhibitory activity against cell proliferation and no nonspecific binding activity to protein were observed. These results indicate that these germacranolides are the specific inhibitors of preadipocyte differentiation.

3T3 Cells↗
PubMed2004

Systematic synthesis of four epicatechin series procyanidin trimers and their inhibitory activity on the Maillard reaction and antioxidant activity.

A systematic synthesis of four natural epicatechin series procyanidin trimers [[4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-cis-3",4"-trans: 2,3-trans-(-)-epi-catechin-(-)-epicatechin-(+)-catechin, [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-cis-3",4"-trans: 2,3-cis-tri-(-)-epicatechin: procyanidin C1, [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-trans-3",4"-trans: 2,3-trans-(-)-epicatechin-(+)-catechin-(+)-catechin: procyanidin C4, and [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-trans-3",4"-trans: 2,3-cis-(-)-epicatechin-(+)-catechin-(-)-epicatechin] is described. Condensation of (2R,3R,4S)-5,7,3'4'-tetra-O-benzyl-4-(2"-ethoxyethyloxy)flavan derived from (-)-epicatechin as an electrophile with the dimeric nucleophiles in the presence of TMSOTf followed by deprotection yielded trimers. Inhibitory activities on the Maillard reaction and antioxidant activity on lipid peroxide of the synthesized oligomers were also investigated.

Antioxidants↗
PubMed2004

Germacranolides from Calea urticifolia.

Four germacranolides, named calealactones A-C and calealactone B [corrected] were isolated from the leaves of Calea urticifolia (Compositae) in addition to three known germacranolides. Their structures were established on the basis of spectroscopic analysis including by 2D NMR spectroscopy. Calealactone C and 2,3-epoxyjuanisulamin displayed potent toxicity to U937 cells.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Ascochlorin derivatives as ligands for nuclear hormone receptors.

Nuclear receptor family proteins are structurally related transcription factors activated by specific lipophilic compounds. Because they are activated by a variety of hormonal molecules, including retinoic acid, vitamin D, and steroid hormones, they are assumed to be promising targets for clinical drugs. We previously found that one ascochlorin (1) derivative, 4-O-carboxymethyl-ascochlorin (2), is a potent agonist of peroxisome proliferator activated receptor gamma (PPARgamma). Here, we synthesized derivatives of 1, designated as a lead compound, to create new modulators of nuclear hormone receptors. Two derivatives, 4-O-carboxymethyl-2-O-methylascochlorin (9) and 4-O-isonicotinoyl-2-O-methylascochlorin (10), showed improved agonistic activity for PPARgamma and induced differentiation of a progenitor cell line, C3H10T1/2. We also found that 1, dehydroascofuranon (29), and a 2,4-O-diacetyl-1-carboxylic acid derivative of 1 (5) specifically activated estrogen receptors, PPARalpha, and an androgen receptor. All of the derivatives (1-29) activated the pregnane X receptor. These results suggest that the chemical structure of 1 is useful in designing novel modulators of nuclear receptors.

Alkenes↗
PubMed2003

Stilbene derivatives from Gnetum gnemon Linn.

Four stilbene derivatives, gnemonols K and L (resveratrol trimers), M (isorhapontigenin dimer), and gnemonoside K (glucoside of resveratrol trimer) together with eleven known stilbenoids and a lignan were isolated from the acetone, methanol and 70% methanol soluble parts of the root of Gnetum gnemon (Gnetaceae). The structures of the isolates were determined by spectral analysis. The antioxidant activity of the stilbenoids on lipid peroxide inhibition and super oxide scavenging activity were also investigated.

Antioxidants↗
PubMed2003

Three new trimeric stilbenes from Gnetum gnemon.

Three stilbene trimers (gnemonols D, E, F) were isolated from the root of Gnetum gnemon. The structures were determined by spectroscopic analysis. In addition, the antioxidant activity of the compounds on lipid peroxide inhibition and super oxide scavenging activity were also investigated.

Gnetum↗
PubMed2002

Usage of tautomycetin, a novel inhibitor of protein phosphatase 1 (PP1), reveals that PP1 is a positive regulator of Raf-1 in vivo.

Protein phosphatase type 1 (PP1), together with protein phosphatase 2A (PP2A), is a major eukaryotic serine/threonine protein phosphatase involved in regulation of numerous cell functions. Although the roles of PP2A have been studied extensively using okadaic acid, a well known inhibitor of PP2A, biological analysis of PP1 has remained restricted because of lack of a specific inhibitor. Recently we reported that tautomycetin (TC) is a highly specific inhibitor of PP1. To elucidate the biological effects of TC, we demonstrated in preliminary experiments that treatment of COS-7 cells with 5 microm TC for 5 h inhibits endogenous PP1 by more than 90% without affecting PP2A activity. Therefore, using TC as a specific PP1 inhibitor, the biological effect of PP1 on MAPK signaling was examined. First, we found that inhibition of PP1 in COS-7 cells by TC specifically suppresses activation of ERK, among three MAPK kinases (ERK, JNK, and p38). TC-mediated inhibition of PP1 also suppressed activation of Raf-1, resulting in the inactivation of the MEK-ERK pathway. To examine the role of PP1 in regulation of Raf-1, we overexpressed the PP1 catalytic subunit (PP1C) in COS-7 cells and found that PP1C enhanced activation of Raf-1 activity, whereas phosphatase-dead PP1C blocked Raf-1 activation. Furthermore, a physical interaction between PP1C and Raf-1 was also observed. These data strongly suggest that PP1 positively regulates Raf-1 in vivo.

Animals↗
PubMed2002

4-isoavenaciolide covalently binds and inhibits VHR, a dual-specificity phosphatase.

A potent inhibitor of a dual-specificity protein phosphatase, VHR (vaccinia H1 related), was isolated during a screening of microbial metabolites. This inhibitor was identified as 4-isoavenaciolide (4-iA), and was determined to irreversibly inhibit VHR phosphatase activity with a 50% inhibitory concentration of 1.2 microM. Detailed tandem mass spectrometry analyses of proteolysed fragments revealed that two molecules of 4-iA bound a molecule of VHR at the two different fragments: one containing the catalytic domain and the other containing the alpha6 helix positioned surface domain. As 4-iA possesses a reactive exo-methylene moiety, it is possible that 4-iA inhibits VHR through the direct binding to the cysteine residue in the catalytic site (Cys124). Furthermore, 4-iA inhibited dual-specificity protein phosphatases and tyrosine phosphatases, but did not inhibit serine/threonine phosphatases. These results suggest that 4-iA is a cysteine-targeting inhibitor of protein phosphatases with a common HCX5RS/T motif in the catalytic site.

Amino Acid Sequence↗
PubMed2002

Bacilysocin, a novel phospholipid antibiotic produced by Bacillus subtilis 168.

We have found a novel phospholipid antibiotic (named bacilysocin) which accumulates within (or associates with) the cells of Bacillus subtilis 168 and determined the structure by nuclear magnetic resonance and mass spectrometry analyses. The structure of bacilysocin elucidated was 1-(12-methyltetradecanoyl)-3-phosphoglyceroglycerol. Bacilysocin demonstrated antimicrobial activity, especially against certain fungi. Production of bacilysocin commenced immediately after growth ceased and before the formation of heat-resistant spores. The production of bacilysocin was completely blocked when the ytpA gene, which encodes a protein homologous to lysophospholipase, was disrupted, but blockage of the ytpA gene did not significantly affect growth. Sporulation was also impaired, with a 10-fold reduction in heat-resistant spore titers being detected. Since the ytpA disruptant actually lacked phospholipase activity, we propose that the YtpA protein functions as an enzyme for the biosynthesis of bacilysocin.

Anti-Bacterial Agents↗
PubMed2002

Indocarbazostatin and indocarbazostatin B, novel inhibitors of NGF-induced neuronal differentiation in PC12 cells. I. Screening, taxonomy, fermentation and biological activities.

During the course of our screening for modulators of signal transduction of mammalian cells, we discovered two novel indolocarbazole antibiotics, indocarbazostatin and indocabazostatin B, from a culture broth of a Streptomyces sp. as inhibitors of NGF-induced neuronal differentiation in rat pheochromocytoma PC12 cells. Indocarbazostatin and indocarbazostatin B inhibited NGF-induced neurite outgrowth from PC12 cells at 6 nM and 24 nM, respectively, whereas K-252a inhibited at 200 nM under our assay conditions.

Animals↗
PubMed2002

Indocarbazostatin and indocarbazostatin B, novel inhibitors of NGF-induced Neuronal differentiation in PC12 cells. II. Isolation, physicochemical properties and structural elucidation.

Two novel indolocarbazol-type bioactive molecules, indocarbazostatin (1) and indocarbazostatin B (2), were isolated as inhibitors of NGF-induced neuronal differentiation in rat pheochromocytoma PC12 cells from a culture broth of a Streptomyces sp. The structures of these compounds were determined by HR-FAB-MS, UV, 1H and 13C NMR, 1H-1H COSY, PFG HMBC, PFG HMQC and DIF NOE experiments. The relative and absolute configurations were deduced from MM2, MOPAC and CONFLEX calculations, and CD analyses. The imide/amide sector rule was proposed from the analyses of CD data of 1 and other indolocarbazole antibiotics. It was concluded that the minor compound 2 has a negative atropisomeric chirality in the aglycone.

Animals↗