Kazuki Ishikawa

Faculty of Pharmaceutical Sciences,Department of Pharmaceutical SciencesLecturer
Last Updated :2025/10/07

■Researcher basic information

Degree

  • Mar. 2016

Field Of Study

  • Life sciences, Environmental and pharmaceutical development resources

■Career

Career

  • Apr. 2024 - Present
    Teikyo Heisei University, Faculty of Pharmaceutical Sciences

Member History

  • Sep. 2021
  • Sep. 2020
  • Sep. 2018

■Research activity information

Award

  • Oct. 2019
  • Apr. 2017
  • Mar. 2017

Paper

  • Synergistic effects of Cyp51 isozyme-specific azole antifungal agents on fungi with multiple cyp51 isozyme genes
    Masaki Ishii; Kazuki Ishikawa; Kazuhiro Mikami; Koji Ichinose; Atsushi Miyashita; Takashi Yaguchi; Tsuyoshi Yamada; Shinya Ohata
    Antimicrobial Agents and Chemotherapy, 26 Sep. 2025
    DOI URL
  • Characterization of ActVI-ORF3 and ActVI-ORF4 as Lactonizing and Delactonizing Enzymes in Relation to Metabolic Flux in Actinorhodin Biosynthesis.
    Makoto Hashimoto; Kazuki Ishikawa; Yuri Fukushima; Sarina Shimazu; Mizuha Yabuzaki; Yuka Kamezawa; Takaaki Taguchi; Koji Ichinose
    Chembiochem : a European journal of chemical biology, 06 Mar. 2025, [Reviewed]
    Actinorhodin (ACT) from Streptomyces coelicolor A3(2) is an aromatic polyketide antibiotic with a benzoisochromanequinone (BIQ) skeleton. Although actVI-ORF3 and actVI-ORF4 are not essential for ACT biosynthesis, homologous genes to these are present in the biosynthetic gene clusters of BIQ lactones. In this study, ActVI-ORF3 was identified as a cofactor-independent enzyme with lactonization activity, using ACT as a substrate. ActVI-ORF3 recognized dihydrokalafungin and 8-hydroxykalafafungin, which share the same pyran-ring configuration as ACT, but not nanaomycin A, which has an opposite configuration. In contrast, ActVI-ORF4 functioned as an NAD(P)-dependent oxidoreductase, catalyzing the delactonization of BIQ lactones. Conversion experiments using isotopically labeled compounds revealed that both lactonization and delactonization reactions of these enzymes yielded products in which the carboxyl oxygen at the C1 position was retained. Subsequently, we reexamined the accumulation of ACT-related compounds in the actVI-ORF3 and actVI-ORF-4 disruptants. The results suggested that ACT intermediates are predominantly pooled in the bacteria as (S)-DNPA rather than in lactone-form. The contribution of ActVI-ORF4 to metabolic flux is not significant, and endogenous reductases can convert these intermediates to the dihydro form, which subsequently re-enters the ACT biosynthetic pathway.
    DOI URL
  • Aszonapyrone A Isolated from Neosartorya spinosa IFM 47025 Inhibits the NF-κB Signaling Pathway Activated by Expression of the Ependymoma-Causing Fusion Protein ZFTA-RELA
    Kazuki Ishikawa; Nao Kamiya; Masaki Ishii; Takashi Yaguchi; Koji Ichinose; Shinya Ohata
    Advances in Microbiology, Sep. 2024, [Reviewed]
    URLDOI URL
  • The Ptk2-Pma1 pathway enhances tolerance to terbinafine in Trichophyton rubrum.
    Masaki Ishii; Tsuyoshi Yamada; Kazuki Ishikawa; Koji Ichinose; Michel Monod; Shinya Ohata
    Antimicrobial agents and chemotherapy, 03 Apr. 2024, [Reviewed]
    The increasing prevalence of dermatophyte resistance to terbinafine, a key drug in the treatment of dermatophytosis, represents a significant obstacle to treatment. Trichophyton rubrum is the most commonly isolated fungus in dermatophytosis. In T. rubrum, we identified TERG_07844, a gene encoding a previously uncharacterized putative protein kinase, as an ortholog of budding yeast Saccharomyces cerevisiae polyamine transport kinase 2 (Ptk2), and found that T. rubrum Ptk2 (TrPtk2) is involved in terbinafine tolerance. In both T. rubrum and S. cerevisiae, Ptk2 knockout strains were more sensitive to terbinafine compared with the wild types, suggesting that promotion of terbinafine tolerance is a conserved function of fungal Ptk2. Pma1 is activated through phosphorylation by Ptk2 in S. cerevisiae. Overexpression of T. rubrum Pma1 (TrPma1) in T. rubrum Ptk2 knockout strain (ΔTrPtk2) suppressed terbinafine sensitivity, suggesting that the induction of terbinafine tolerance by TrPtk2 is mediated by TrPma1. Furthermore, omeprazole, an inhibitor of plasma membrane proton pump Pma1, increased the terbinafine sensitivity of clinically isolated terbinafine-resistant strains. These findings suggest that, in dermatophytes, the TrPtk2-TrPma1 pathway plays a key role in promoting intrinsic terbinafine tolerance and may serve as a potential target for combinational antifungal therapy against terbinafine-resistant dermatophytes.
    DOI URL
  • Actinorhodin Biosynthesis Terminates with an Unprecedented Biaryl Coupling Reaction.
    Makoto Hashimoto; Susumu Watari; Takaaki Taguchi; Kazuki Ishikawa; Takuya Kumamoto; Susumu Okamoto; Koji Ichinose
    Angewandte Chemie (International ed. in English), 02 Dec. 2022, [Reviewed]
    A plethora of dimeric natural products exist with diverse chemical structures and biological activities. A major strategy for dimerization is aryl coupling reactions catalyzed by cytochrome P450 or laccase. Actinorhodin (ACT) from Streptomyces coelicolor has a dimeric pyranonaphthoquinone structure connected by a C-C bond. Here, we identified a NmrA-family dimerizing enzyme, ActVA-ORF4, and a cofactor independent oxidase, ActVA-ORF3, both involved in the last step of ACT biosynthesis. ActVA-ORF4 is a unique  NAD(P)H-dependent enzyme that catalyzes the inter-molecular C-C bond formation using 8-hydroxydihydrokalafungin (DHK-OH) as the sole substrate. On the other hand, ActVA-ORF3 was found to be a quinone-forming enzyme that produces the coupling substrate, DHK-OH, and the final product, ACT. Consequently, the functional assignment of all essential enzymes in ACT biosynthesis was completed, which would be a landmark in our understanding of the entire biosynthetic pathway for one of the best-known model natural products, ACT.
    DOI URL
  • Characterization of stereospecific enoyl reductase ActVI-ORF2 for pyran ring formation in the actinorhodin biosynthesis of Streptomyces coelicolor A3(2).
    Kazuki Ishikawa; Makoto Hashimoto; Kunpei Komatsu; Takaaki Taguchi; Susumu Okamoto; Koji Ichinose
    Bioorganic & medicinal chemistry letters, 15 Jun. 2022, [Reviewed]
    Actinorhodin (ACT) is a benzoisochromanequinone antibiotic produced by Streptomyces coelicolor A3(2), which has served as a favored model organism for comprehensive studies of antibiotic biosynthesis and its regulation. (S)-DNPA undergoes various modifications as an intermediate in the ACT biosynthetic pathway, including enoyl reduction to DDHK. It has been suggested that actVI-ORF2 encodes an enoyl reductase (ER). However, its function has not been characterized in vitro. In this study, biochemical analysis of recombinant ActVI-ORF2 revealed that (S)-DNPA is converted to DDHK in a stereospecific manner with NADPH acting as a cofactor. (R)-DNPA was also reduced to 3-epi-DDHK with the comparable efficacy as (S)-DNPA, suggesting that the stereospecificity of ActVI-ORF2 was not affected by the stereochemistry at the C-3 of DNPA. ActVI-ORF2 is a new example of a discrete ER, which is distantly related to known ERs according to phylogenetic analysis.
    DOI URL
  • epi-Aszonalenin B from Aspergillus novofumigatus inhibits NF-κB activity induced by ZFTA-RELA fusion protein that drives ependymoma.
    Kazuki Ishikawa; Masaki Ishii; Takashi Yaguchi; Toshiaki Katada; Koji Ichinose; Shinya Ohata
    Biochemical and biophysical research communications, 12 Mar. 2022, [Reviewed]
    Nuclear factor-kappa B (NF-κB) signaling is an intracellular signaling pathway involved in inflammatory responses and the pathogenesis of various cancers, including ependymoma, which is a rare and chemotherapy-resistant glioma. Several isoforms of fusion proteins that consist of a nuclear protein, zinc finger translocation associated (ZFTA), and RELA (ZFTA-RELA), an NF-κB-signaling effector transcription factor, cause excessive activation of the NF-κB signaling pathway and result in supratentorial ependymomas (ST-EPN-RELA). As inhibitors of NF-κB activity induced by ZFTA-RELA are expected to be therapeutic agents for ST-EPN-RELA, we established an NF-κB responsive luciferase reporter cell line that expresses the most common isoform of ZFTA-RELA in a doxycycline-dependent manner. Using this reporter cell line, we screened fungus extracts for compounds that inhibit the NF-κB activity induced by ZFTA-RELA expression and identified aszonalenin, an alkaloid from Aspergillus novofumigatus. We also purified analogs of aszonalenin, namely acetylaszonalenin and epi-aszonalenin B and C. In a luciferase assay using cells constitutively expressing luciferase (counter assay), acetylaszonalenin and epi-aszonalenin C showed non-specific inhibition of the luciferase activity. Aszonalenin and epi-aszonalenin B inhibited the NF-κB responsive luciferase activity by expressing ZFTA-RELA more strongly than the luciferase activity in the counter assay. The upregulation of endogenous NF-κB responsive genes, such as CCND1, ICAM1, and L1CAM, by ZFTA-RELA expression was inhibited by epi-aszonalenin B, but not by aszonalenin. This study suggests that epi-aszonalenin B may be a lead compound for the therapeutic development of ST-EPN-RELA.
    DOI URL
  • Identification of Blue-colored Substances in TLC Analysis of ‘Sanshishi’ Extracts: An Application of Basic Research Result Aimed at Improving Learning Effectiveness in Chemical Laboratory Practice of Pharmacognosy
    石川和樹; 八木諒人; 田口貴章; 橋元誠; 馬場本絵未; 市瀬浩志
    生薬学雑誌, 2021, [Reviewed]
  • Cover Feature: Unveiling Two Consecutive Hydroxylations: Mechanisms of Aromatic Hydroxylations Catalyzed by Flavin‐Dependent Monooxygenases for the Biosynthesis of Actinorhodin and Related Antibiotics (ChemBioChem 5/2020)
    Makoto Hashimoto; Takaaki Taguchi; Kazuki Ishikawa; Ryuichiro Mori; Akari Hotta; Susumu Watari; Kazuaki Katakawa; Takuya Kumamoto; Susumu Okamoto; Koji Ichinose
    ChemBioChem, 02 Mar. 2020, [Invited]
    URLDOI URL
  • Unveiling Two Consecutive Hydroxylations: Mechanisms of Aromatic Hydroxylations Catalyzed by Flavin-Dependent Monooxygenases for the Biosynthesis of Actinorhodin and Related Antibiotics.
    Makoto Hashimoto; Takaaki Taguchi; Kazuki Ishikawa; Ryuichiro Mori; Akari Hotta; Susumu Watari; Kazuaki Katakawa; Takuya Kumamoto; Susumu Okamoto; Koji Ichinose
    Chembiochem : a European journal of chemical biology, 02 Mar. 2020, [Reviewed]
    Flavin-dependent monooxygenases are ubiquitous in living systems and are classified into single- or two-component systems. Actinorhodin, produced by Streptomyces coelicolor, is a representative polycyclic polyketide that is hydroxylated through the action of the two-component ActVA-5/ActVB hydroxylase system. These homologous systems are widely distributed in bacteria, but their reaction mechanisms remain unclear. This in vitro investigation has provided chemical proof of two consecutive hydroxylations via hydroxynaphthalene intermediates involved in actinorhodin biosynthesis. The ActVA-5 oxygenase component catalyzed a stepwise dihydroxylation of the substrate, whereas the ActVB flavin reductase not only supplied a reduced cofactor, but also regulated the quinone-hydroquinone interconversion of an intermediate. Our study provides clues for understanding the general biosynthetic mechanisms of highly functionalized aromatic natural products with structural diversity.
    DOI URL
  • Antifungal Activity of Compounds Isolated from Bamboo Vermicompost against Rhizoctonia solani AG1-IB　　　　　　　　　　　　　　　
    Xiaodong You; Daigo Wakana; Kazuki Ishikawa; Tomoo Hosoe; Motoaki Tojo
    Advances in Microbiology, Dec. 2019, [Reviewed]
  • Antimicrobial agent isolated from Coptidis rhizome extract incubated with Rhodococcus sp. strain BD7100.
    Kazuki Ishikawa; Kazunori Takahashi; Syun Hosoi; Hisashi Takeda; Hinaka Yoshida; Daigo Wakana; Masayoshi Tsubuki; Fumihiko Sato; Motoaki Tojo; Tomoo Hosoe
    The Journal of antibiotics, Feb. 2019, [Reviewed]
    Coptidis rhizome (CR) is a widely used herbal medicine that contains protoberberine-type alkaloids. CR extract exhibits various pharmacologic activities. A previous study reported the isolation of Rhodococcus sp. strain BD7100 as a berberine (BBR)-utilizing bacterium, and the BBR-degradation pathway has been investigated. When we incubated strain BD7100 cells with CR extract, the number of viable cells declined with the degradation of components in the CR extract, and the culture broth exhibited antibacterial activity against strain BD7100. These results suggest that CR extract cultured in the presence of strain BD7100 contains one or more antibacterial agents. In this study, we isolated coptirhoquinone A (1) from CR extract incubated with strain BD7100 in Luria-Bertani (LB) medium, and the structure was elucidated using NMR and MS analysis. We also report the total synthesis and antimicrobial activities of 1 against bacteria, fungi, and Pythium sp.
    DOI URL
  • FOUR CYCLODIPEPTIDES, ASNOVOLENINS A-B AND ASNOVOZINES A-B, FROM ASPERGILLUS NOVOFUMIGATUS
    Ishikawa Kazuki; Wakana Daigo; Itabashi Takeshi; Takeda Hisashi; Yaguchi Takashi; Kawai Ken-ichi; Hosoe Tomoo
    HETEROCYCLES, 01 Jun. 2018, [Reviewed]
    DOI URLScopus URLScopus Citedby URL
  • A new cinnamoylphenethylamine derivative from a Mongolian Allium species, Allium carolinianum
    Tsutomu Tsuruoka; Kazuki Ishikawa; Tomoo Hosoe; Darikhand Davaajab; Suvd Duvjir; Unursaikhan Surenjav
    Journal of Natural Medicines, 01 Jan. 2018, [Reviewed]
    DOI URL
  • Common origin of methylenedioxy ring degradation and demethylation in bacteria
    Hisashi Takeda; Kazuki Ishikawa; Hinaka Yoshida; Daisuke Kasai; Daigo Wakana; Masao Fukuda; Fumihiko Sato; Tomoo Hosoe
    SCIENTIFIC REPORTS, Aug. 2017, [Reviewed]
    DOI URL
  • Asnovolins A-G, Spiromeroterpenoids Isolated from the Fungus Aspergillus novofumigatus, and Suppression of Fibronectin Expression by Asnovolin E
    Kazuki Ishikawa; Fumiaki Sato; Takeshi Itabashi; Hiroshi Wachi; Hisashi Takeda; Daigo Wakana; Takashi Yaguchi; Ken-ichi Kawai; Tomoo Hosoe
    JOURNAL OF NATURAL PRODUCTS, Sep. 2016, [Reviewed]
    DOI URL
  • Isolation and identification of berberine and berberrubine metabolites by berberine-utilizing bacterium Rhodococcus sp strain BD7100
    Kazuki Ishikawa; Hisashi Takeda; Daigo Wakana; Fumihiko Sato; Tomoo Hosoe
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY, May 2016, [Reviewed]
    DOI URL
  • 11-Hydroxylation of Protoberberine by the Novel Berberine-Utilizing Aerobic Bacterium Sphingobium sp Strain BD3100
    Hisashi Takeda; Kazuki Ishikawa; Daigo Wakana; Masao Fukuda; Fumihiko Sato; Tomoo Hosoe
    JOURNAL OF NATURAL PRODUCTS, Dec. 2015, [Reviewed]
    DOI URL
  • Quinazolinobenzodiazepine derivatives, novobenzomalvins A-C: Fibronectin expression regulators from Aspergillus novofumigatus
    Kazuki Ishikawa; Tomoo Hosoe; Takeshi Itabashi; Fumiaki Sato; Hiroshi Wachi; Hiromasa Nagase; Takashi Yaguchi; Ken-Ichi Kawai
    Scientia Pharmaceutica, 2011, [Reviewed]
    DOI URL
  • A NOVOFUMIGATAMIDE, NEW CYCLIC TRIPEPTIDE FROM ASPERGILLUS NOVOFUMIGATUS
    Kazuki Ishikawa; Tomoo Hosoe; Takeshi Itabashi; Kayoko Takizawa; Takashi Yaguchi; Ken-ichi Kawai
    HETEROCYCLES, Sep. 2010, [Reviewed]
    DOI URL
  • Novoamauromine and ent-Cycloechinulin: Two New Diketopiperazine Derivatives from Aspergillus novofumigatus
    Kazuki Ishikawa; Tomoo Hosoe; Takeshi Itabashi; Daigo Wakana; Kayoko Takizawa; Takashi Yaguchi; Ken-ichi Kawai
    CHEMICAL & PHARMACEUTICAL BULLETIN, May 2010, [Reviewed]
    DOI URL

MISC

Lectures, oral presentations, etc.

Affiliated academic society

  • SOCIETY FOR ACTINOMYCETES JAPAN　　　　　　　　　　　　　　　
  • THE MYCOLOGICAL SOCIETY OF JAPAN　　　　　　　　　　　　　　　
  • THE JAPANESE SOCIETY OF PHARMACOGNOSY　　　　　　　　　　　　　　　
  • THE PHARMACEUTICAL SOCIETY OF JAPAN