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Nobuyasu Matsuura

Publications and source records attributed to Nobuyasu Matsuura.

13 recordsLinked to original sources
PubMed2006

A novel enzyme conferring streptothricin resistance alters the toxicity of streptothricin D from broad-spectrum to bacteria-specific.

Streptothricins (STs) produced by Streptomyces strains are broad-spectrum antibiotics. All STs consist of a carbamoylated D-gulosamine to which the beta-lysine homopolymer (1 to 7 residues) and the amide form of the unusual amino acid streptolidine (streptolidine lactam) are attached. Although many ST-resistance genes have been identified in bacteria, including clinically isolated pathogens and ST-producing Streptomyces strains, only one resistance mechanism has been identified to date. This mechanism involves the modification of the ST molecule by monoacetylation of the moiety of the beta-lysine(s). In this study, we successfully isolated a novel ST-resistance gene (sttH) from Streptomyces albulus, which is a known ST nonproducer. The in vitro analysis of SttH demonstrated that this enzyme catalyzes the hydrolysis of the amide bond of streptolidine lactam, thereby conferring ST resistance. Interestingly, the selective toxicity of ST-D possessing 3x beta-lysine moiety was altered from broad-spectrum to bacteria-specific by the hydrolysis of streptolidine lactam, although ST-F (1 x beta-lysine) was detoxified by SttH in both prokaryotes and eukaryotes (yeasts). STs have not been clinically developed due to their toxicities; however, in this study, we showed that hydrolyzed ST-D (ST-D-acid) exhibits potent antibacterial activity even when its toxicity against eukaryotic cells is reduced by SttH. This suggests that ST-D-acid is a potential candidate for clinical development or for use as a new lead compound for drug discovery.

Bacterial Proteins↗
PubMed2005

A potent apoptosis-inducing activity of a sesquiterpene lactone, arucanolide, in HL60 cells: a crucial role of apoptosis-inducing factor.

Six main sesquiterpene lactones (germacranolides) from Calea urticifolia were evaluated for in vitro cytotoxicity against human tumor cell lines HL60 and SW480 cells. Among them, arucanolide and parthenolide displayed marked cytotoxicity against both cell lines. Arucanolide exhibited a low IC(50) in HL60 cells. The cytotoxic activity of arucanolide was observed at lower concentrations compared to that of parthenolide, which has been reported to be a typical and simple germacranolide. The activity was found to be mainly due to apoptosis that was assessed by morphological findings, DNA ladder formation (24 - 36 h), and flow cytometric analysis in HL60 cells. Western blotting and an apoptosis inhibition assay using caspase inhibitors did not demonstrate the activation of any caspases tested. However, the mitochondrial membrane potential of HL60 cells was lost after 24-h treatment with arucanolide, and concurrently apoptosis-inducing factor (AIF) released from mitochondria was detected by Western blot analysis. The inactivation of nuclear factor-kappaB, which has been commonly shown in parthenolide-induced apoptosis, did not occur in arucanolide-induced apoptosis. Taken together, the findings presented here indicate that arucanolide induced marked apoptosis in HL60 cells mainly by dissipating mitochondrial membrane potential, which would trigger AIF-induced apoptosis.

Antineoplastic Agents, Phytogenic↗
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↗
PubMed2004

Presence of copalyl diphosphate synthase gene in an actinomycete possessing the mevalonate pathway.

We have previously shown that gene clusters for biosyntheses of terpentecin and BE-40644, a diterpene antibiotic and a sesquiterpene antibiotic, respectively, were located in the adjacent mevalonate pathway gene clusters. In this study, a mevalonate pathway gene cluster was cloned from Streptomyces sp. strain KO-3988, which was known to produce furaquinocin A, employing a hybridization experiment using a 3-hydroxy-3-methyl glutaryl CoA (HMG-CoA) reductase gene, which had been previously cloned from the strain KO-3988, as a probe. By sequencing flanking regions, we found four open reading frames that could encode a putative cytochrome P450 (ORF1), an isoprenoid cyclase (ORF2), an unknown protein (ORF3), and a polyprenyl diphosphate synthase gene (ORF4) in the upstream region of the mevalonate pathway gene cluster, though we did not find any genes related to furaquinocin A biosynthesis. The two ORFs (ORF2 and 4) were expressed as recombinant enzymes in E. coli and used for studies to investigate functions of these products. The ORF4 product was confirmed to be a geranylgeranyl diphosphate (GGDP, C20) synthase. The ORF2 product proved to catalyze a conversion of GGDP into copalyl diphosphate, the first example of an enzyme with this function of prokaryotic origin. These results again showed that actinomycetes possessing the mevalonate pathway usually produce an isoprenoid and that its biosynthetic gene cluster exists in adjacent the mevalonate pathway gene cluster.

Alkyl and Aryl Transferases↗
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

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↗