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Articles by T Katayama
Total Records ( 5 ) for T Katayama
  J Endo , M Sano , T Katayama , T Hishiki , K Shinmura , S Morizane , T Matsuhashi , Y Katsumata , Y Zhang , H Ito , Y Nagahata , S Marchitti , K Nishimaki , A. M Wolf , H Nakanishi , F Hattori , V Vasiliou , T Adachi , I Ohsawa , R Taguchi , Y Hirabayashi , S Ohta , M Suematsu , S Ogawa and K. Fukuda

Rationale: Aldehyde accumulation is regarded as a pathognomonic feature of oxidative stress–associated cardiovascular disease.

Objective: We investigated how the heart compensates for the accelerated accumulation of aldehydes.

Methods and Results: Aldehyde dehydrogenase 2 (ALDH2) has a major role in aldehyde detoxification in the mitochondria, a major source of aldehydes. Transgenic (Tg) mice carrying an Aldh2 gene with a single nucleotide polymorphism (Aldh2*2) were developed. This polymorphism has a dominant-negative effect and the Tg mice exhibited impaired ALDH activity against a broad range of aldehydes. Despite a shift toward the oxidative state in mitochondrial matrices, Aldh2*2 Tg hearts displayed normal left ventricular function by echocardiography and, because of metabolic remodeling, an unexpected tolerance to oxidative stress induced by ischemia/reperfusion injury. Mitochondrial aldehyde stress stimulated eukaryotic translation initiation factor 2 phosphorylation. Subsequent translational and transcriptional activation of activating transcription factor-4 promoted the expression of enzymes involved in amino acid biosynthesis and transport, ultimately providing precursor amino acids for glutathione biosynthesis. Intracellular glutathione levels were increased 1.37-fold in Aldh2*2 Tg hearts compared with wild-type controls. Heterozygous knockout of Atf4 blunted the increase in intracellular glutathione levels in Aldh2*2 Tg hearts, thereby attenuating the oxidative stress–resistant phenotype. Furthermore, glycolysis and NADPH generation via the pentose phosphate pathway were activated in Aldh2*2 Tg hearts. (NADPH is required for the recycling of oxidized glutathione.)

Conclusions: The findings of the present study indicate that mitochondrial aldehyde stress in the heart induces metabolic remodeling, leading to activation of the glutathione–redox cycle, which confers resistance against acute oxidative stress induced by ischemia/reperfusion.

  H Ashida , A Miyake , M Kiyohara , J Wada , E Yoshida , H Kumagai , T Katayama and K. Yamamoto

Bifidobacteria are predominant bacteria present in the intestines of breast-fed infants and offer important health benefits for the host. Human milk oligosaccharides are one of the most important growth factors for bifidobacteria and are frequently fucosylated at their non-reducing termini. Previously, we identified 1,2--l-fucosidase (AfcA) belonging to the novel glycoside hydrolase (GH) family 95, from Bifidobacterium bifidum JCM1254 (Katayama T, Sakuma A, Kimura T, Makimura Y, Hiratake J, Sakata K, Yamanoi T, Kumagai H, Yamamoto K. 2004. Molecular cloning and characterization of Bifidobacterium bifidum 1,2--l-fucosidase (AfcA), a novel inverting glycosidase (glycoside hydrolase family 95). J Bacteriol. 186:4885–4893). Here, we identified a gene encoding a novel 1,3–1,4--l-fucosidase from the same strain and termed it afcB. The afcB gene encodes a 1493-amino acid polypeptide containing an N-terminal signal sequence, a GH29 -l-fucosidase domain, a carbohydrate binding module (CBM) 32 domain, a found-in-various-architectures (FIVAR) domain and a C-terminal transmembrane region, in this order. The recombinant enzyme was expressed in Escherichia coli and was characterized. The enzyme specifically released 1,3- and 1,4-linked fucosyl residues from 3-fucosyllactose, various Lewis blood group substances (a, b, x, and y types), and lacto-N-fucopentaose II and III. However, the enzyme did not act on glycoconjugates containing 1,2-fucosyl residue or on synthetic -fucoside (p-nitrophenyl--l-fucoside). The afcA and afcB genes were introduced into the B. longum 105-A strain, which has no intrinsic -l-fucosidase. The transformant carrying afcA could utilize 2'-fucosyllactose as the sole carbon source, whereas that carrying afcB was able to utilize 3-fucosyllactose and lacto-N-fucopentaose II. We suggest that AfcA and AfcB play essential roles in degrading 1,2- and 1,3/4-fucosylated milk oligosaccharides, respectively, and also glycoconjugates, in the gastrointestinal tracts.

  M Miwa , T Horimoto , M Kiyohara , T Katayama , M Kitaoka , H Ashida and K. Yamamoto

Bifidobacteria are predominant in the intestines of breast-fed infants and offer health benefits to the host. Human milk oligosaccharides (HMOs) are considered to be one of the most important growth factors for intestinal bifidobacteria. HMOs contain two major structures of core tetrasaccharide: lacto-N-tetraose (Galβ1-3GlcNAcβ1-3Galβ1-4Glc; type 1 chain) and lacto-N-neotetraose (Galβ1-4GlcNAcβ1-3Galβ1-4Glc; type 2 chain). We previously identified the unique metabolic pathway for lacto-N-tetraose in Bifidobacterium bifidum. Here, we clarified the degradation pathway for lacto-N-neotetraose in the same bifidobacteria. We cloned one β-galactosidase (BbgIII) and two β-N-acetylhexosaminidases (BbhI and BbhII), all of which are extracellular membrane-bound enzymes. The recombinant BbgIII hydrolyzed lacto-N-neotetraose into Gal and lacto-N-triose II, and furthermore the recombinant BbhI, but not BbhII, catalyzed the hydrolysis of lacto-N-triose II to GlcNAc and lactose. Since BbgIII and BbhI were highly specific for lacto-N-neotetraose and lacto-N-triose II, respectively, they may play essential roles in degrading the type 2 oligosaccharides in HMOs.

  M Watanabe , M Yumoto , H Tanaka , H. H Wang , T Katayama , S Yoshiyama , J Black , S. E Thatcher and K. Kohama

To explore the precise mechanisms of the inhibitory effects of blebbistatin, a potent inhibitor of myosin II, on smooth muscle contraction, we studied the blebbistatin effects on the mechanical properties and the structure of contractile filaments of skinned (cell membrane permeabilized) preparations from guinea pig taenia cecum. Blebbistatin at 10 µM or higher suppressed Ca2+-induced tension development at any given Ca2+ concentration but had little effects on the Ca2+-induced myosin light chain phosphorylation. Blebbistatin also suppressed the 10 and 2.75 mM Mg2+-induced, "myosin light chain phosphorylation-independent" tension development at more than 10 µM. Furthermore, blebbistatin induced conformational change of smooth muscle myosin (SMM) and disrupted arrangement of SMM and thin filaments, resulting in inhibition of actin-SMM interaction irrespective of activation with Ca2+. In addition, blebbistatin partially inhibited Mg2+-ATPase activity of native actomyosin from guinea pig taenia cecum at around 10 µM. These results suggested that blebbistatin suppressed skinned smooth muscle contraction through disruption of structure of SMM by the agent.

  R Suzuki , T Katayama , M Kitaoka , H Kumagai , T Wakagi , H Shoun , H Ashida , K Yamamoto and S. Fushinobu

Endo--N-acetylgalactosaminidase (endo--GalNAc-ase), a member of the glycoside hydrolase (GH) family 101, hydrolyses the O-glycosidic bonds in mucin-type O-glycan between -GalNAc and Ser/Thr. Endo--GalNAc-ase from Bifidobacterium longum JCM1217 (EngBF) is highly specific for the core 1-type O-glycan to release the disaccharide Galβ1-3GalNAc (GNB), whereas endo--GalNAc-ase from Clostridium perfringens (EngCP) exhibits broader substrate specificity. We determined the crystal structure of EngBF at 2.0 Å resolution and performed automated docking analysis to investigate possible binding modes of GNB. Mutational analysis revealed important residues for substrate binding, and two Trp residues (Trp748 and Trp750) appeared to form stacking interactions with the β-faces of sugar rings of GNB by substrate-induced fit. The difference in substrate specificities between EngBF and EngCP is attributed to the variations in amino acid sequences in the regions forming the substrate-binding pocket. Our results provide a structural basis for substrate recognition by GH101 endo--GalNAc-ases and will help structure-based engineering of these enzymes to produce various kinds of neo-glycoconjugates.

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