Ushio Sankawa
University of Tokyo
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Featured researches published by Ushio Sankawa.
Journal of Natural Products | 2006
Ghazi Hussein; Ushio Sankawa; Hirozo Goto; Kinzo Matsumoto; Hiroshi Watanabe
Astaxanthin (1), a red-orange carotenoid pigment, is a powerful biological antioxidant that occurs naturally in a wide variety of living organisms. The potent antioxidant property of 1 has been implicated in its various biological activities demonstrated in both experimental animals and clinical studies. Compound 1 has considerable potential and promising applications in human health and nutrition. In this review, the recent scientific literature (from 2002 to 2005) is covered on the most significant activities of 1, including its antioxidative and anti-inflammatory properties, its effects on cancer, diabetes, the immune system, and ocular health, and other related aspects. We also discuss the green microalga Haematococcus pluvialis, the richest source of natural 1, and its utilization in the promotion of human health, including the antihypertensive and neuroprotective potentials of 1, emphasizing our experimental data on the effects of dietary astaxanthin on blood pressure, stroke, and vascular dementia in animal models, is described.
Chemistry & Biology | 2001
Isao Fujii; Akira Watanabe; Ushio Sankawa; Yutaka Ebizuka
BACKGROUND Based on the homology with fatty acid synthases and bacterial polyketide synthases (PKSs), thioesterase domains have been assigned at the C-terminus regions of fungal iterative type I PKSs. We previously overexpressed Aspergillus nidulans wA PKS gene in a heterologous fungal host and identified it to encode a heptaketide naphthopyrone synthase. In addition, expression of C-terminus-modified WA PKS gave heptaketide isocoumarins suggesting that the C-terminus region of WA PKS is involved in the cyclization of the second aromatic ring of naphthopyrone. To unravel the actual function of the C-terminus region, we carried out functional analysis of WA PKS mutants by C-terminus deletion and site-directed mutagenesis. RESULTS Only the 32 amino acid deletion from the C-terminus of WA PKS caused product change to heptaketide isocoumarins from heptaketide naphthopyrone, YWA1 1, a product of intact WA PKS. Further C-terminus deletion mutant of WA PKS up to Ser(1967), an active site residue of so far called thioesterase, still produced isocoumarins. Site-directed mutagenesis of amino acid residues in this C-terminus region showed that even a single mutation of S1967A or H2129Q caused production of isocoumarin instead of naphthopyrone. Furthermore, the role of tandem acyl carrier proteins (ACPs), a typical feature of fungal aromatic PKSs, was examined by site-directed mutagenesis and the results indicated that both ACPs can function as ACP independently. CONCLUSIONS Claisen-type cyclization is assumed to be involved in formation of aromatic compounds by some fungal type I PKSs. These PKSs have a quite identical architecture of active site domain organization, beta-ketoacyl synthase, acyltransferase, tandem ACPs and thioesterase (TE) domains. Since the C-terminus region of WA PKS of this type was determined to be involved in Claisen-type cyclization of the second ring of naphthopyrone, we propose that the so far called TE of these PKSs work not just as TE but as Claisen cyclase.
Molecular Genetics and Genomics | 1996
Isao Fujii; Y. Ono; H. Tada; Katsuya Gomi; Yutaka Ebizuka; Ushio Sankawa
Abstract Southern blot analysis of genomic DNAs of several fungi that produce polyketide compounds with the 6-methylsalicylic acid synthase (MSAS) gene of Penicillium patulum as a probe indicated the presence of an MSAS-homologous gene in the (+)-geodin-producing strain IMI 16043 of Aspergillus terreus. The gene, designated atX was cloned from an A. terreus genomic DNA library and 7588 bp of the gene together with its flanking regions were sequenced to reveal the presence of a 5.5 kb open reading frame coding for a protein of 1800 amino acids with 190 kDa molecular mass. The presence of a short (70 bp) intron near the N-terminus of the atX gene was predicted that contains the canonical GT and AG dinucleotides at its 5′- and 3′-splicing junctions. The predicted ATX polypeptide showed high homology with P. patulum MSAS along the whole sequence. On the other hand, slight homology was detected only around the β-ketoacyl synthase regions of Aspergillus nidulans wA, PKSST and Colletotrichum lagenarium PKS1. No transcription of atX was observed throughout the culture period by Northern blotting analysis. To identify the function of the polypeptide encoded by the atX gene, its coding region was introduced into the fungal expression vector pTAex3 under the control of the amyB promoter. The constructed expression plasmid was introduced into A. nidulans. The transformant produced significant amounts of 6-methylsalicylic acid, the structure of which was identified by physicochemical analysis. This result unambiguously demonstrated that the atX gene codes for MSAS of A. terreus.
Tetrahedron Letters | 1999
Akira Watanabe; Isao Fujii; Ushio Sankawa; María E. Mayorga; William E. Timberlake; Yutaka Ebizuka
Abstract By reconstruction and expression of the full-length WA (NWA) polyketide synthase of A. nidulans based on the revised wA gene sequence, its product was re-identified to be a naphthopyrone compound YWA1 instead of citreoisocoumarin and its derivatives, which were found to be products of C-terminus truncated WA polyketide synthase. YWA1 shows yellow color and is considered to be a true intermediate of A. nidulans asexual spore pigments. Thus, the wA gene is identified to code for a polyketide synthase of heptaketide naphthopyrone YWA1.
Tetrahedron Letters | 1998
Akira Watanabe; Yuya Ono; Isao Fujii; Ushio Sankawa; María E. Mayorga; William E. Timberlake; Yutaka Ebizuka
Abstract The WA gene cloned from A. nidulans which was assumed to code for polyketide synthase involved in conidial spore pigment biosynthesis was expressed in a heterologous host fungus A. oryzae using starch inducible fungal expression plasmid pTAex3. The A. oryzae transformant produced starch inducible compounds, whose structures were identified to be citreoisocoumairn and its derivatives. Apparent heptaketide nature of these compounds identified that the wA gene codes for a heptaketide synthase of A. nidulans .
FEBS Letters | 1999
Toshio Yamaguchi; Fumiya Kurosaki; Dae-Yeon Suh; Ushio Sankawa; Mizue Nishioka; Takumi Akiyama; Masaaki Shibuya; Yutaka Ebizuka
Chalcone synthase (CHS) and stilbene synthase (STS) are related plant polyketide synthases belonging to the CHS superfamily. CHS and STS catalyze common condensation reactions of p‐coumaroyl‐CoA and three C2‐units from malonyl‐CoA but different cyclization reactions to produce naringenin chalcone and resveratrol, respectively. Using purified Pueraria lobata CHS and Arachis hypogaea STS overexpressed in Escherichia coli, bisnoryangonin (BNY, the derailed lactone after two condensations) and p‐coumaroyltriacetic acid lactone (the derailed lactone after three condensations) were detected from the reaction products. More importantly, we found a cross‐reaction between CHS and STS, i.e. resveratrol production by CHS (2.7–4.2% of naringenin) and naringenin production by STS (1.4–2.3% of resveratrol), possibly due to the conformational flexibility of their active sites.
Journal of Biological Chemistry | 1995
Ke-xue Huang; Isao Fujii; Yutaka Ebizuka; Katsuya Gomi; Ushio Sankawa
Aspergillus terreus dihydrogeodin oxidase (DHGO) is an enzyme catalyzing the stereospecific phenol oxidative coupling reaction converting dihydrogeodin to (+)-geodin. We previously reported the purification of DHGO from A. terreus and raised polyclonal antibody against DHGO. From the first cDNA library constructed in gt11 using mRNA from 3-day-old mycelium of A. terreus, four clones were identified using anti-DHGO antibody, but all contained partial cDNA inserts around 280 base pairs. This cDNA fragment was used as a probe to clone the genomic DNA and cDNA for dihydrogeodin oxidase from A. terreus. The sequence of the cloned DHGO genomic DNA and cDNA predicted that the DHGO polypeptide consists of 605 amino acids showing significant homology with multicopper blue proteins such as laccase and ascorbate oxidase. Four potential copper binding domains exist in DHGO polypeptide. The DHGO gene consists of seven exons separated by six short introns. Expression of the DHGO gene in Aspergillus nidulans under the starch or maltose-inducible Taka-amylase A promoter as an active enzyme established the functional identity of the gene. Also, introduction of the genomic DNA for DHGO into Penicillium frequentans led to the production of DHGO polypeptide as judged by Western blot analysis.
Phytochemistry | 1988
Kurnia Firman; Takeshi Kinoshita; Akiko Itai; Ushio Sankawa
Abstract A new guaiane sesquiterpene named oxycurcumenol was isolated from the steam-distilled essential oil fraction of Curcuma heyneana in addition to known sesquiterpenes germacrone, dehydrocurdione, isocurcumenol, curcumenol, curcumanolide A, B and zerumbone. Its structure was elucidated on the basis of spectroscopic and chemical studies, and finally confirmed by X-ray crystallography. ( E )-Labda-8(17),12-diene-15,16-dial was isolated from the benzene extract of the same plant together with dehydrocurdione, curcumenol, curcumanolide A and B. The taxonomic status of C. heyneana is briefly discussed based on the chemotaxonomic significance of these findings.
Tetrahedron | 1973
Nobuhiro Takeda; Shujiro Seo; Yukio Ogihara; Ushio Sankawa; I. Iitaka; Isao Kitagawa; Shoji Shibata
Abstract The structures of (+)rugulosin, (−)luteoskyrin and (−)rubroskyrin have been reexamined by NMR and new structures 18, 19 and 20 proposed respectively. Their absolute structures were established on the basis of the X-ray analysis of (+)dibromodehydrotetrahydrorugulosin (27). The minor analogous metabolites, (−)4a-oxyluteoskyrin (31) of P. islandicum and (+)4a-oxyrugulosin (32) of P. brunneum, have been formulated. On oxidation of (−)luteoskyrin and (+)rugulosin with pertrifluoroacetic acid (−)4a,4a′-dioxyluteoskyrin (33) and (+>4a,4a′-dioxyrugulosin (34) were formed, while with MnO2 (+)4a,4a′-dehydrorugulosin (35) was obtained. The structures of lumiluteoskyrin (37), and deoxylumiluteoskyrin (38), photooxidation products of luteoskyrin and deoxyluteoskyrin, respectively, have been elucidated.
Phytochemistry | 1998
Takashi Hakamatsuka; Kazumi Mori; Shinichi Ishida; Yutaka Ebizuka; Ushio Sankawa
Abstract 2-Hydroxyisoflavanone dehydratase, which catalyzes the final step of the formation of the isoflavonoid skeleton, was purified and characterized from yeast extract-elicited cell suspension cultures of Pueraria lobata. 2-Hydroxyisoflavanone, the substrate of the dehydratase, is the product of 2-hydroxyisoflavanone synthase, as cytochrome P-450 which catalyzes the hydroxylation step associated with aryl migration of flavanone. The dehydratase was purified to apparent homogeneity for the first time by a seven-step purification procedure. It is a single polypeptide with a molecular weight of 38 kDa, and has an isoelectric point at pH 5.1 and a pH optimum at 6.8. It required no co-factor, and the apparent Michaelis constant for 2,7,4′-trihydroxyisoflavanone was 7.0 mM.