Research activity information

• Dynamic regulation of the chloroplast SUFBC2D complex by SUFB expression and CLP protease in Arabidopsis
  Yuting Cheng; Zhaoyang Liu; Bing Yang; Qingsong Jiao; Hisashi Ito; Atsushi Takabayashi; Ryouichi Tanaka; Ting Jia; Xueyun Hu
  Journal of Experimental Botany, 17 Mar. 2026
  Scientific journal
• Chelatase activity of magnesium dechelatase associated with chlorophyll degradation
  Soma Sato; Mitsuaki Hirose; Hitoshi Tamiaki; Hisashi Ito
  FEBS Letters, Wiley, 17 Jun. 2025, [Peer-reviewed], [Corresponding author]
  Scientific journal, Metalated tetrapyrrole molecules play crucial roles in respiration, photosynthesis, and biocatalysis. In this study, the chelatase activity of the bacterial magnesium dechelatase homologous gene, which encodes an enzyme that extracts the central magnesium ion from chlorophyll, was demonstrated. The recombinant protein inserted metal ions, such as zinc, into methyl pyropheophorbide a, a synthetic derivative of chlorophyll a. Mutation analysis and structural modeling suggested H32, D34, and D62 as key residues involved in coordinating metal ions and facilitating proton extraction from methyl pyropheophorbide a. Chelatase activity was also found in the recombinant plant magnesium dechelatase protein. The bacterial gene complemented Escherichia coli ferrochelatase mutants. These findings provide novel insights into the mechanisms underlying chelation reactions.
• Activity examination of plant Mg-dechelatase and its bacterial homolog in plants and in vitro
  Saki Ando; Ryouichi Tanaka; Hisashi Ito
  Plant Physiology and Biochemistry, Oct. 2024, [Peer-reviewed], [Corresponding author]
  Scientific journal
• Structural Characterization of the Chlorophyllide a Oxygenase (CAO) Enzyme Through an In Silico Approach
  Dey, D.; Tanaka, R.; Ito, H.
  Journal of Molecular Evolution, 91, 2, 2023, [Peer-reviewed], [Corresponding author]
  Scientific journal
• Heterologous complementation systems verify the mosaic distribution of three distinct protoporphyrinogen IX oxidase in the cyanobacterial phylum
  Ryoya Kohata; HyunSeok Lim; Yuki Kanamoto; Akio Murakami; Yuichi Fujita; Ayumi Tanaka; Wesley Swingley; Hisashi Ito; Ryouichi Tanaka
  Journal of Plant Research, 136, 1, 107, 115, Springer Science and Business Media LLC, 10 Nov. 2022, [Peer-reviewed]
  English, Scientific journal
• Poplar leaf abscission through induced chlorophyll breakdown by Mg-dechelatase
  Hisashi Ito; Hideyuki Saito; Manabu Fukui; Ayumi Tanaka; Keita Arakawa
  Plant Science, 324, 111444, 111444, Elsevier BV, Nov. 2022, [Peer-reviewed], [Corresponding author]
  Scientific journal
• Crystal structure and reaction mechanism of a bacterial Mg-dechelatase homolog from the Chloroflexi Anaerolineae.
  Debayan Dey; Masayoshi Nishijima; Ryouichi Tanaka; Genji Kurisu; Hideaki Tanaka; Hisashi Ito
  Protein science : a publication of the Protein Society, 31, 10, e4430, Oct. 2022, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal, Chlorophyll degradation plays a myriad of physiological roles in photosynthetic organisms, including acclimation to light environment and nutrient remobilization during senescence. Mg extraction from chlorophyll a is the first and committed step of the chlorophyll degradation pathway. This reaction is catalyzed by the Mg-dechelatase enzyme encoded by Stay-Green (SGR). The reaction mechanism of SGR protein remains elusive since metal ion extraction from organic molecules is not a common enzymatic reaction. Additionally, experimentally derived structural information about SGR or its homologs has not yet been reported. In this study, the crystal structure of the SGR homolog from Anaerolineae bacterium was determined using the molecular replacement method at 1.85 Å resolution. Our previous study showed that three residues-H32, D34, and D62 are essential for the catalytic activity of the enzyme. Biochemical analysis involving mutants of D34 residue further strengthened its importance in the functioning of the dechelatase. Docking simulation also revealed the interaction between the D34 side chain and central Mg ion of chlorophyll a. Structural analysis showed the arrangement of D34/H32/D62 in the form of a catalytic triad that is generally found in hydrolases. The probable reaction mechanism suggests that deprotonated D34 side chain coordinates and destabilizes Mg, resulting in Mg extraction. Besides, H32 possibly acts as a general base catalyst and D62 facilitates H32 to be a better proton acceptor. Taken together, the reaction mechanism of SGR partially mirrors the one observed in hydrolases.
• Characterization of photosystem II assembly complexes containing ONE-HELIX PROTEIN1 in Arabidopsis thaliana.
  Hanaki Maeda; Koharu Takahashi; Yoshifumi Ueno; Kei Sakata; Akari Yokoyama; Kozue Yarimizu; Fumiyoshi Myouga; Kazuo Shinozaki; Shin-Ichiro Ozawa; Yuichiro Takahashi; Ayumi Tanaka; Hisashi Ito; Seiji Akimoto; Atsushi Takabayashi; Ryouichi Tanaka
  Journal of plant research, 135, 2, 361, 376, Mar. 2022, [Peer-reviewed], [Domestic magazines]
  English, Scientific journal, The assembly process of photosystem II (PSII) requires several auxiliary proteins to form assembly intermediates. In plants, early assembly intermediates comprise D1 and D2 subunits of PSII together with a few auxiliary proteins including at least ONE-HELIX PROTEIN1 (OHP1), OHP2, and HIGH-CHLOROPHYLL FLUORESCENCE 244 (HCF244) proteins. Herein, we report the basic characterization of the assembling intermediates, which we purified from Arabidopsis transgenic plants overexpressing a tagged OHP1 protein and named the OHP1 complexes. We analyzed two major forms of OHP1 complexes by mass spectrometry, which revealed that the complexes consist of OHP1, OHP2, and HCF244 in addition to the PSII subunits D1, D2, and cytochrome b559. Analysis of chlorophyll fluorescence showed that a major form of the complex binds chlorophyll a and carotenoids and performs quenching with a time constant of 420 ps. To identify the localization of the auxiliary proteins, we solubilized thylakoid membranes using a digitonin derivative, glycodiosgenin, and separated them into three fractions by ultracentrifugation, and detected these proteins in the loose pellet containing the stroma lamellae and the grana margins together with two chlorophyll biosynthesis enzymes. The results indicated that chlorophyll biosynthesis and assembly may take place in the same compartments of thylakoid membranes. Inducible suppression of the OHP2 mRNA substantially decreased the OHP2 protein in mature Arabidopsis leaves without a significant reduction in the maximum quantum yield of PSII under low-light conditions, but it compromised the yields under high-light conditions. This implies that the auxiliary protein is required for acclimation to high-light conditions.
• Enrichment of chlorophyll catabolic enzymes in grana margins and their cooperation in catabolic reactions.
  Koki Fukura; Ayumi Tanaka; Ryouichi Tanaka; Hisashi Ito
  Journal of plant physiology, 266, 153535, 153535, 25 Sep. 2021, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal, During leaf senescence, chlorophyll a and b are degraded through several enzymatic reactions, including chlorophyll b reductase, 7-hydroxymethyl chlorophyll a reductase, and Mg-dechelatase. Considering that the intermediates of the chlorophyll breakdown pathway are highly photoreactive, cooperative and efficient reactions of chlorophyll metabolic enzymes may protect chloroplasts from potential photo-oxidative damage. Here, we investigated the sub-organellar localization and cooperative reactions of the enzymes involved in the chlorophyll breakdown pathway by the fractionation of thylakoid membranes and enzymatic assays using recombinant proteins. We found that these enzymes were enriched in the grana margin fraction. Furthermore, we found that chlorophyll b reductase and Mg-dechelatase efficiently catabolized chlorophylls bound to the chlorophyll-protein complexes when these two enzymes were mixed. These results suggest that the co-localization of chlorophyll catabolic enzymes enables efficient chlorophyll breakdown. The results from this study highlight a key step forward in the investigation of the photosystem breakdown process.
• Distribution and functional analysis of the two types of 8-vinyl reductase involved in chlorophyll biosynthesis in marine cyanobacteria.
  Haruka Suehiro; Ryouichi Tanaka; Hisashi Ito
  Archives of microbiology, 203, 6, 3565, 3575, Aug. 2021, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal, In the chlorophyll biosynthesis pathway, the 8-vinyl group of the chlorophyll precursor is reduced to an ethyl group by 8-vinyl reductase. Two isozymes of 8-vinyl reductase have been described in oxygenic photosynthetic organisms: one encoded by BciA and another by BciB. Only BciB contains an [Fe-S] cluster and most cyanobacteria harbor this form; whereas a few contain BciA. Given this disparity in distribution, cyanobacterial BciA has remained largely overlooked, which has limited understanding of chlorophyll biosynthesis in these microorganisms. Here, we reveal that cyanobacterial BciA encodes a functional 8-vinyl reductase, as evidenced by measuring the in vitro activity of recombinant Synechococcus and Acaryochloris BciA. Genomic comparison revealed that BciB had been replaced by BciA during evolution of the marine cyanobacterium Synechococcus, and coincided with replacement of Fe-superoxide dismutase (SOD) with Ni-SOD. These findings imply that the acquisition of BciA confers an adaptive advantage to cyanobacteria living in low-iron oceanic environments.
• Degradation of the photosystem II core complex is independent of chlorophyll degradation mediated by Stay-Green Mg2+ dechelatase in Arabidopsis.
  Ying Chen; Wataru Yamori; Ayumi Tanaka; Ryouichi Tanaka; Hisashi Ito
  Plant science : an international journal of experimental plant biology, 307, 110902, 110902, Jun. 2021, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal, During leaf senescence, the degradation of photosystems and photosynthetic pigments proceeds in a coordinated manner, which would minimize the potential photodamage to cells. Both photosystem I and II are composed of core complexes and peripheral antenna complexes, with the former binding chlorophyll a and the latter binding chlorophyll a and b. Although the degradation of peripheral antenna complexes is initiated by chlorophyll degradation, it remains unclear whether the degradation of core complexes and chlorophyll is coordinated. In this study, we examined the degradation of peripheral antenna and core complexes in the Arabidopsis sgr1/sgr2/sgrl triple mutant, lacking all the isoforms of chlorophyll a:Mg2+ dechelatase. In this mutant, the degradation of peripheral antenna complexes and photosystem I core complexes was substantially retarded, but the core complexes of photosystem II were rapidly degraded during leaf senescence. On the contrary, the photosynthetic activity declined at a similar rate as in the wild type plants. These results suggest that the degradation of photosystem II core complexes is regulated independently of the major chlorophyll degradation pathway mediated by the dechelatase. The study should contribute to the understanding of the complex molecular mechanisms underlying the degradation of photosystems, which is an essential step during leaf senescence.
• Insights into the structure and function of the rate-limiting enzyme of chlorophyll degradation through analysis of a bacterial Mg-dechelatase homolog
  Debayan Dey; Dipanjana Dhar; Helena Fortunato; Daichi Obata; Ayumi Tanaka; Ryouichi Tanaka; Soumalee Basu; Hisashi Ito
  Computational and Structural Biotechnology Journal, 19, 5333, 5347, Jan. 2021, [Peer-reviewed], [Corresponding author]
  Scientific journal
• Natural variations at the Stay-Green gene promoter control lifespan and yield in rice cultivars.
  Dongjin Shin; Sichul Lee; Tae-Heon Kim; Jong-Hee Lee; Joonheum Park; Jinwon Lee; Ji Yoon Lee; Lae-Hyeon Cho; Jae Young Choi; Wonhee Lee; Ji-Hwan Park; Dae-Woo Lee; Hisashi Ito; Dae Heon Kim; Ayumi Tanaka; Jun-Hyeon Cho; You-Chun Song; Daehee Hwang; Michael D Purugganan; Jong-Seong Jeon; Gynheung An; Hong Gil Nam
  Nature communications, 11, 1, 2819, 2819, 04 Jun. 2020, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Increased grain yield will be critical to meet the growing demand for food, and could be achieved by delaying crop senescence. Here, via quantitative trait locus (QTL) mapping, we uncover the genetic basis underlying distinct life cycles and senescence patterns of two rice subspecies, indica and japonica. Promoter variations in the Stay-Green (OsSGR) gene encoding the chlorophyll-degrading Mg++-dechelatase were found to trigger higher and earlier induction of OsSGR in indica, which accelerated senescence of indica rice cultivars. The indica-type promoter is present in a progenitor subspecies O. nivara and thus was acquired early during the evolution of rapid cycling trait in rice subspecies. Japonica OsSGR alleles introgressed into indica-type cultivars in Korean rice fields lead to delayed senescence, with increased grain yield and enhanced photosynthetic competence. Taken together, these data establish that naturally occurring OsSGR promoter and related lifespan variations can be exploited in breeding programs to augment rice yield.
• In vitro enzymatic activity assays implicates the existence of the chlorophyll cycle in chlorophyll b-containing cyanobacteria.
  Lim H; Tanaka A; Tanaka R; Ito H
  Plant & cell physiology, Aug. 2019, [Peer-reviewed], [Corresponding author]
• Horizontal transfer of promiscuous activity from non-photosynthetic bacteria contributed to evolution of chlorophyll degradation pathway.
  Obata D; Takabayashi A; Tanaka R; Tanaka A; Ito H
  Molecular biology and evolution, Aug. 2019, [Peer-reviewed], [Corresponding author]
• Jasmonate production through chlorophyll a degradation by Stay-Green in Arabidopsis thaliana.
  Ono K; Kimura M; Matsuura H; Tanaka A; Ito H
  Journal of plant physiology, 238, 53, 62, Jul. 2019, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal, Leaf color change through chlorophyll degradation is a characteristic symptom of senescence. Magnesium removal from chlorophyll a is the initial step in chlorophyll a degradation, in a reaction catalyzed by Stay-Green (SGR). Arabidopsis thaliana has three SGR homologs, SGR1, SGR2, and SGR-like. When SGR1 is overexpressed, both chlorophyll a and b are degraded and leaves turn yellow. This process is visually identical to senescence, suggesting that SGR1 overexpression affects various physiological processes in plants. To examine this possibility, gene expression associated with chlorophyll metabolism and senescence was analyzed following dexamethasone-inducible SGR1 introduction into Arabidopsis. When SGR1 was overexpressed following 18 h of dexamethasone treatment, genes involved in chlorophyll degradation were upregulated, as were senescence-associated genes. These observations suggested that chlorophyll a degradation promotes senescence. As jasmonate is the plant hormone responsible for senescence and was expected to be involved in the regulation of gene expression after dexamethasone treatment, the level of jasmonoyl-isoleucine, the active form of jasmonate, was measured. The jasmonoyl-isoleucine level increased slightly after 10 h of SGR1 overexpression, and this increase became significant after 18 h. These observations suggest that jasmonate is produced through chlorophyll a degradation and affects the promotion of senescence.
• Mg-dechelatase is involved in the formation of photosystem II but not in chlorophyll degradation in Chlamydomonas reinhardtii.
  Chen Y; Shimoda Y; Yokono M; Ito H; Tanaka A
  The Plant journal : for cell and molecular biology, 97, 6, 1022, 1031, Mar. 2019, [Peer-reviewed], [Corresponding author]
• Mg-dechelation of chlorophyll a by Stay-Green activates chlorophyll b degradation through expressing Non-Yellow Coloring 1 in Arabidopsis thaliana
  Tomoaki Sato; Yousuke Shimoda; Kaori Matsuda; Ayumi Tanaka; Hisashi Ito
  Journal of Plant Physiology, 222, 94, 102, Elsevier GmbH, 01 Mar. 2018, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• The Non-Mendelian Green Cotyledon Gene in Soybean Encodes a Small Subunit of Photosystem II
  Kaori Kohzuma; Yutaka Sato; Hisashi Ito; Ayako Okuzaki; Mai Watanabe; Hideki Kobayashi; Michiharu Nakano; Hiroshi Yamatani; Yu Masuda; Yumi Nagashima; Hiroyuki Fukuoka; Tetsuya Yamada; Akira Kanazawa; Keisuke Kitamura; Yutaka Tabei; Masahiko Ikeuchi; Wataru Sakamoto; Ayumi Tanaka; Makoto Kusaba
  PLANT PHYSIOLOGY, 173, 4, 2138, 2147, Apr. 2017, [Peer-reviewed]
  English, Scientific journal
• Chlorophyll a is a favorable substrate for Chlamydomonas Mg-dechelatase encoded by STAY-GREEN
  Kaori Matsuda; Yousuke Shimoda; Ayumi Tanaka; Hisashi Ito
  PLANT PHYSIOLOGY AND BIOCHEMISTRY, 109, 365, 373, Dec. 2016, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• Simultaneous regulation of antenna size and photosystem I/II stoichiometry in Arabidopsis thaliana
  Ting Jia; Hisashi Ito; Ayumi Tanaka
  PLANTA, 244, 5, 1041, 1053, Nov. 2016, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• Arabidopsis STAY-GREEN, Mendel's Green Cotyledon Gene, Encodes Magnesium-Dechelatase
  Yousuke Shimoda; Hisashi Ito; Ayumi Tanaka
  PLANT CELL, 28, 9, 2147, 2160, Sep. 2016, [Peer-reviewed]
  English, Scientific journal
• Chlorophyll b degradation by chlorophyll b reductase under high-light conditions
  Rei Sato; Hisashi Ito; Ayumi Tanaka
  PHOTOSYNTHESIS RESEARCH, 126, 2-3, 249, 259, Dec. 2015, [Peer-reviewed]
  English, Scientific journal
• Functional characterization of the FNT family nitrite transporter of marine picocyanobacteria
  Shin-Ichi Maeda; Akio Murakami; Hisashi Ito; Ayumi Tanaka; Tatsuo Omata
  Life, 5, 1, 432, 446, MDPI AG, 09 Feb. 2015, [Peer-reviewed]
  English, Scientific journal
• Accumulation of the NON-YELLOW COLORING 1 protein of the chlorophyll cycle requires chlorophyll b in Arabidopsis thaliana
  Ting Jia; Hisashi Ito; Xueyun Hu; Ayumi Tanaka
  PLANT JOURNAL, 81, 4, 586, 596, Feb. 2015, [Peer-reviewed]
  English, Scientific journal
• The Chlorophyll b Reductase NOL Participates in Regulating the Antenna Size of Photosystem II in Arabidopsis Thaliana.
  Jia T; Ito H; Tanaka A
  Procedia Chemistry, 14, 422, 427, 2015, [Peer-reviewed]
  English, Scientific journal
• Evolution of a New Chlorophyll Metabolic Pathway Driven by the Dynamic Changes in Enzyme Promiscuous Activity
  Hisashi Ito; Ayumi Tanaka
  PLANT AND CELL PHYSIOLOGY, 55, 3, 593, 603, Mar. 2014, [Peer-reviewed]
  English, Scientific journal
• Protein co-migration database (PCoM -DB) for Arabidopsis thylakoids and Synechocystis cells
  Atsushi Takabayashi; Ryosuke Kadoya; Masayoshi Kuwano; Katsunori Kurihara; Hisashi Ito; Ryouichi Tanaka; Ayumi Tanaka
  SPRINGERPLUS, 2, 1, 148, 2013, [Peer-reviewed]
  English, Scientific journal
• Conversion of chlorophyll b to chlorophyll a precedes magnesium dechelation for protection against necrosis in Arabidopsis
  Yousuke Shimoda; Hisashi Ito; Ayumi Tanaka
  PLANT JOURNAL, 72, 3, 501, 511, Nov. 2012, [Peer-reviewed]
  English, Scientific journal
• Chlorophyll b Reductase Plays an Essential Role in Maturation and Storability of Arabidopsis Seeds
  Saori Nakajima; Hisashi Ito; Ryouichi Tanaka; Ayumi Tanaka
  PLANT PHYSIOLOGY, 160, 1, 261, 273, Sep. 2012, [Peer-reviewed]
  English, Scientific journal
• Luminescence of singlet oxygen in photosystem II complexes isolated from cyanobacterium Synechocystis sp. PCC6803 containing monovinyl or divinyl chlorophyll a.
  Tomo T; Kusakabe H; Nagao R; Ito H; Tanaka A; Akimoto S; Mimuro M; Okazaki S
  Biochimica et biophysica acta, 1817, 1299, 1305, 8, Aug. 2012, [Peer-reviewed]
• Luminescence of singlet oxygen in photosystem II complexes isolated from cyanobacterium Synechocystis sp PCC6803 containing monovinyl or divinyl chlorophyll a
  Tatsuya Tomo; Hayato Kusakabe; Ryo Nagao; Hisashi Ito; Ayumi Tanaka; Seiji Akimoto; Mamoru Mimuro; Shigetoshi Okazaki
  BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1817, 8, 1299, 1305, Aug. 2012, [Peer-reviewed]
  English, Scientific journal
• How Did the Chlorophyll Biosynthetic Pathways Get Diversified?
  伊藤 寿; 田中 歩; 田中 亮一
  光合成研究, 22, 2, 98, 105, 日本光合成学会, Aug. 2012
  Japanese
• 珪藻のクロロフィル合成系の解析
  伊藤寿; 田中歩
  藻類, 60, 2, 117, 10 Jul. 2012
  Japanese
• Alterations in photosynthetic pigments and amino acid composition of D1 protein change energy distribution in photosystem II.
  Yokono M; Tomo T; Nagao R; Ito H; Tanaka A; Akimoto S
  Biochimica et biophysica acta, 1817, 754, 759, 5, May 2012, [Peer-reviewed]
• Alterations in photosynthetic pigments and amino acid composition of D1 protein change energy distribution in photosystem II
  Makio Yokono; Tatsuya Tomo; Ryo Nagao; Hisashi Ito; Ayumi Tanaka; Seiji Akimoto
  BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1817, 5, 754, 759, May 2012, [Peer-reviewed]
  English, Scientific journal
• Chlorophyll Metabolism in Photosynthetic Organisms
  Tanaka, R.; Takabayashi, A.; Ito, H.; Tanaka, A.
  Handbook of Porphyrin Science: With Applications to Chemistry, Physics, Materials Science, Engineering, Biology and Medicine: Volume 16 - 20: Synthetic Developments: Part I, 16-20, 2012
  Scientific journal
• Evolution of a divinyl chlorophyll-based photosystem in Prochlorococcus
  Hisashi Ito; Ayumi Tanaka
  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 108, 44, 18014, 18019, Nov. 2011, [Peer-reviewed]
  English, Scientific journal
• Identification of the 7-Hydroxymethyl Chlorophyll a Reductase of the Chlorophyll Cycle in Arabidopsis
  Miki Meguro; Hisashi Ito; Atsushi Takabayashi; Ryouichi Tanaka; Ayumi Tanaka
  PLANT CELL, 23, 9, 3442, 3453, Sep. 2011, [Peer-reviewed]
  English, Scientific journal
• Participation of Chlorophyll b Reductase in the Initial Step of the Degradation of Light-harvesting Chlorophyll a/b-Protein Complexes in Arabidopsis
  Yukiko Horie; Hisashi Ito; Makoto Kusaba; Ryouichi Tanaka; Ayumi Tanaka
  JOURNAL OF BIOLOGICAL CHEMISTRY, 284, 26, 17449, 17456, Jun. 2009, [Peer-reviewed]
  English, Scientific journal
• Replacement of chlorophyll with di-vinyl chlorophyll in the antenna and reaction center complexes of the cyanobacterium Synechocystis sp PCC 6803: Characterization of spectral and photochemical properties
  Tatsuya Tomo; Seiji Akimoto; Hisashi Ito; Tohru Tsuchiya; Michitaka Fukuya; Ayumi Tanaka; Mamoru Mimuro
  BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1787, 3, 191, 200, Mar. 2009, [Peer-reviewed]
  English, Scientific journal
• Replacement of chlorophyll with di-vinyl chlorophyll in the antenna and reaction center complexes of the cyanobacterium Synechocystis sp. PCC 6803: characterization of spectral and photochemical properties.
  Tomo T; Akimoto S; Ito H; Tsuchiya T; Fukuya M; Tanaka A; Mimuro M
  Biochimica et biophysica acta, 1787, 3, 191, 200, Mar. 2009, [Peer-reviewed]
• Identification of a novel vinyl reductase gene essential for the biosynthesis of monovinyl chlorophyll in Synechocystis sp PCC6803
  Hisashi Ito; Makio Yokono; Ryouichi Tanaka; Ayumi Tanaka
  JOURNAL OF BIOLOGICAL CHEMISTRY, 283, 14, 9002, 9011, Apr. 2008, [Peer-reviewed]
  English, Scientific journal
• Rice NON-YELLOW COLORING1 is involved in light-harvesting complex II and grana degradation during leaf senescence
  Makoto Kusaba; Hisashi Ito; Ryouhei Morita; Shuichi Iida; Yutaka Sato; Masaru Fujimoto; Shinji Kawasaki; Ryouichi Tanaka; Hirohiko Hirochika; Minoru Nishimura; Ayumi Tanaka
  PLANT CELL, 19, 4, 1362, 1375, Apr. 2007, [Peer-reviewed]
  English, Scientific journal
• High light inhibits chlorophyll biosynthesis at the level of 5-aminolevulinate synthesis during de-etiolation in cucumber (Cucumis sativus) cotyledons
  D. Aarti; R. Tanaka; H. Ito; A. Tanaka
  PHOTOCHEMISTRY AND PHOTOBIOLOGY, 83, 1, 171, 176, Jan. 2007, [Peer-reviewed]
  English, Scientific journal
• 海産藻類の光合成系と生産性の再評価 海洋性ラン藻ProchlorococcusとSynechococcusの光合成と進化
  伊藤寿; 永田望; 田中歩
  月刊海洋, 38, 6, 417, 424, 01 Jun. 2006
  Japanese

• 全ゲノムの比較によるラン藻のジビニルクロロフィル還元酵素の同定と解析
  伊藤寿; 横野牧生; 田中亮一; 田中歩, 日本植物生理学会年会要旨集, 49th, 231, 15 Mar. 2008
  Japanese
• クロロフィルの生合成
  田中 歩; 田中 亮一; 伊藤 寿, 蛋白質核酸酵素, 41, 2, 136, 145, Feb. 1996
  共立出版, Japanese

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• クロロフィルを分解するマグネシウム脱離酵素の触媒機構の解明
  科学研究費助成事業
  01 Apr. 2023 - 31 Mar. 2026
  伊藤 寿
  植物の光合成に使われるクロロフィルは地球上でもっとも量の多い色素であり、1年に約1億トン合成され分解されている。これだけ顕著な反応にもかかわらずクロロフィルの分解を律速するマグネシウム（Mg）脱離酵素(クロロフィルの中心金属のMgを外す)の触媒機構は分かっていない。類似した反応がないためである。つまり、有機物から金属を外すという酵素反応はまれなものであり、その触媒機構の解明は重要な意義を持つ。そうした中、我々は最近Mg脱離酵素の構造決定に成功した。これにより、触媒機構の解明を現実的な課題として設定できる段階になった。本研究の目的は（1）側鎖を修飾した様々なクロロフィルに対する活性、（2）活性部位のアミノ酸置換体の解析、（3）酵素と基質の共結晶化、を検討することによりMg脱離酵素の触媒機構を解明することである。酵素の触媒機構の解明は生物学において常に基本的で重要な課題である。本研究は、有機物から金属を外すという新規性の高い酵素の触媒機構を明らかにすることを目標としている。
  今年度は、側鎖を修飾した様々なクロロフィルの類縁体を作製し、それらに対する活性の測定を中心に研究を進めた。その結果、金属に配位している窒素をまずプロトンが攻撃し、窒素と中心金属の配位結合が切れ、その結果中心金属が外れることが示唆された。合わせて酵素と基質の結晶化も進めた。この共結晶化の検討においても、クロロフィルの側鎖や中心金属を改変したものを作製し利用した。活性部位のアミノ酸置換体の解析については、変異体の作成を行った。
  日本学術振興会, 基盤研究(C), 北海道大学, 23K05691