Kyushu University Academic Staff Educational and Research Activities Database
Researcher information (To researchers) Need Help? How to update
Keishi Sakaguchi Last modified date:2019.08.20

Associate Professor / Fisheries Research Institute of Karatsu, Department of Joint Research
Faculty of Agriculture

Academic Degree
Field of Specialization
Molecular Biology, Biochemistry, bioengineering
Outline Activities
* Development molecular techniques applicable to aquaculture industry
Research Interests
  • Study on Structure and Function of Glycosphingolipid-specific Glycohydrolase and Glycosyltransferase
    keyword : glycosphinglipid, sphingolipid-degrading enzyme, catalytic mechanism, glycosyltransferase, in vivo function, zebrafish, knockdown
  • Study on structure-function relationship of seaweed polysaccharide degrading enzyme(s)
    keyword : seaweed polysacchride degrading enzyme, catalytic mechanism, X-ray crystal structure analysis
  • Study on a HUFA-synthesizing machinery of marine thraustochytrids
    keyword : thraustochytrids, transformation system, genetic modification, highly-unsaturated fatty acids, DHA, EPA, genome analysis, biofuel
  • Studies on the development of the efficient aquaculture methods
    keyword : genetically modified animal, genome editing, animal factory, model animal, aquaculture
Academic Activities
1. Sakaguchi K, Kiyohara M, Watanabe N, Yamaguchi K, Ito M, Kawamura T, Tanaka I., Preparation and preliminary X-ray analysis of the catalytic module of beta-1,3-xylanase from the marine bacterium Vibrio sp. AX-4., Acta Crystallogr D Biol Crystallogr., 10.1107/S0907444904013411, 60, Pt 8, 1470-1472, 2004.08.
2. Kiyohara M, Sakaguchi K, Yamaguchi K, Araki T, Nakamura T, Ito M., Molecular cloning and characterization of a novel beta-1,3-xylanase possessing two putative carbohydrate-binding modules from a marine bacterium Vibrio sp. strain AX-4., Biochem J., 10.1042/BJ20050190, 388, Pt 3, 949-957, 2005.06.
3. Kiyohara M, Sakaguchi K, Yamaguchi K, Araki T, Ito M., Characterization and application of carbohydrate-binding modules of beta-1,3-xylanase XYL4., J Biochem., 146, 5, 633-641, 2009.11.
4. Kobayashi T, Sakaguchi K, Matsuda T, Abe E, Hama Y, Hayashi M, Honda D, Okita Y, Sugimoto S, Okino N, Ito M., Increase of eicosapentaenoic acid in thraustochytrids through thraustochytrid ubiquitin promoter-driven expression of a fatty acid {delta}5 desaturase gene., Appl Environ Microbiol., 77, 11, 3870-3876, 2011.01.
5. Goddard-Borger ED, Sakaguchi K, Reitinger S, Watanabe N, Ito M, Withers SG., Mechanistic insights into the 1,3-xylanases: useful enzymes for manipulation of algal biomass., J Am Chem Soc., 134, 8, 3895-3902, 2012.02, Xylanases capable of degrading the crystalline microfibrils of 1,3-xylan that reinforce the cell walls of some red and siphonous green algae have not been well studied, yet they could prove to be of great utility in algaculture for the production of food and renewable chemical feedstocks. To gain a better mechanistic understanding of these enzymes, a suite of reagents was synthesized and evaluated as substrates and inhibitors of an endo-1,3-xylanase. With these reagents, a retaining mechanism was confirmed for the xylanase, its catalytic nucleophile identified, and the existence of −3 to +2 substrate-binding subsites demonstrated. Protein crystal X-ray diffraction methods provided a high resolution structure of a trapped covalent glycosyl–enzyme intermediate, indicating that the 1,3-xylanases likely utilize the 1S3 → 4H3 → 4C1 conformational itinerary to effect catalysis.
6. Sakaguchi K, Matsuda T, Kobayashi T, Ohara J, Hamaguchi R, Abe E, Nagano N, Hayashi M, Ueda M, Honda D, Okita Y, Taoka Y, Sugimoto S, Okino N, Ito M., Versatile transformation system that is applicable to both multiple transgene expression and gene targeting for Thraustochytrids., Appl Environ Microbiol., 78, 9, 3193-3202, 2012.05, ould be used in the transformation system. A neomycin resistance gene (neo(r)), driven with an ubiquitin or an EF-1α promoter-terminator from Thraustochytrium aureum ATCC 34304, was introduced into representatives of two thraustochytrid genera, Aurantiochytrium and Thraustochytrium. The neo(r) marker was integrated into the chromosomal DNA by random recombination and then functionally translated into neo(r) mRNA. Additionally, we confirmed that another two genera, Parietichytrium and Schizochytrium, could be transformed by the same method. By this method, the enhanced green fluorescent protein was functionally expressed in thraustochytrids. Meanwhile, T. aureum ATCC 34304 could be transformed by two 18S ribosomal DNA-targeting vectors, designed to cause single- or double-crossover homologous recombination. Finally, the fatty acid Δ5 desaturase gene was disrupted by double-crossover homologous recombination in T. aureum ATCC 34304, resulting in an increase of dihomo-γ-linolenic acid (C(20:3n-6)) and eicosatetraenoic acid (C(20:4n-3)), substrates for Δ5 desaturase, and a decrease of arachidonic acid (C(20:4n-6)) and eicosapentaenoic acid (C(20:5n-3)), products for the enzyme. These results clearly indicate that a versatile transformation system which could be applicable to both multiple transgene expression and gene targeting was established for thraustochytrids.
7. Matsuda T, Sakaguchi K, Hamaguchi R, Kobayashi T, Abe E, Hama Y, Hayashi M, Honda D, Okita Y, Sugimoto S, Okino N, Ito M., Analysis of Δ12-fatty acid desaturase function revealed that two distinct pathways are active for the synthesis of PUFAs in T. aureum ATCC 34304., J Lipid Res., 53, 6, 1210-1222, 2012.06.
8. Junichiro Ohara, Keishi Sakaguchi, Yuji Okita, NOZOMU OKINO, Makoto Ito, Two fatty acid elongases possessing C18-D6/C18-D9/C20-D5 or C16-D9 elongase activity in Thraustochytrium sp. ATCC 26185., Marine Biotechnology, 15, 4, 476-486, 2013.08.
Membership in Academic Society
  • The Japanese Society of Fisheries Science
  • Japan Society for Bioscience, Biotechnology, and Agrochemistry
  • Japanese Society for Marine Biotechnology