Asian Science Citation Index is committed to provide an authoritative, trusted and significant information by the coverage of the most important and influential journals to meet the needs of the global scientific community.  
ASCI Database
308-Lasani Town,
Sargodha Road,
Faisalabad, Pakistan
Fax: +92-41-8815544
Contact Via Web
Suggest a Journal
 
Articles by K Minoura
Total Records ( 2 ) for K Minoura
  R Takahashi , S Nakamura , T Nakazawa , K Minoura , T Yoshida , Y Nishi , Y Kobayashi and T. Ohkubo
 

Nicotinamide (NM) phosphoribosyltransferase (NMPRTase) catalyzes the reaction of NM and 5'-phosphoribosyl-1'-pyrophosphate (PRPP) to form NM mononucleotide (NMN) and pyrophosphate (PPi) in the pathway of NAD-biosynthesis. Monitoring the 1H and 31P NMR spectra of the reaction mixture, we found that this reaction is reversible as dictated by the equilibrium constant K = [NMN][PPi]/([NM][PRPP]) = 0.14, which agreed well with the ratio of second-order rate constants for forward and backward reactions, K = 0.16. The crystal structures of this enzyme in the free form and bound to NM and PRPP at the resolution of 2.0–2.2 Å were essentially identical to that of the complex with NMN, except for some variations that could facilitate the substitution reaction by fixing the nucleophile and the leaving group for the requisite inversion of configuration at the C1’ carbon of the ribose ring. In the active site near the C1’ atom of the bound PRPP or NMN, there was neither negatively charged group nor waterproof environment necessary to support the feasibility of a ribo-oxocarbocation intermediate inherent in the SN1 mechanism. The structures and catalytic mechanism thus revealed are also discussed in connection with the multiple biological functions of NMPRTase.

  C Nishiura , K Takeuchi , K Minoura , M Sumida , T Taniguchi , K Tomoo and T. Ishida
 

The inhibition of tau fibrillation is a potential therapeutic target for Alzheimer’s and other neurodegenerative diseases. As a series of studies on inhibiting the transition of soluble monomeric tau into mature fibril, the effect of Tyr310 residue in the third repeat (R3) of the microtubule-binding domain (MBD) on the assembly of MBD was investigated using Tyr-substituted MBD mutants by fluorescence, circular dichroism spectroscopy and electron microscopy. Consequently, the importance of the Tyr residue located at position 310, not at other positions, was clearly shown. The conformational comparison of the Tyr310Ala-substituted R3 repeat peptide with the unsubstituted one showed that the Tyr residue contributes to the rigid extended structure of the N-terminal V306QIVYK311 sequence, and its replacement by Ala leads to the deformation of the extended structure, consequently losing its aggregation ability. The present results indicate that a compound that interacts specifically with the Tyr residue or an antibody recognizing the region containing the Tyr residue becomes a candidate for inhibiting tau fibrillation.

 
 
 
Copyright   |   Desclaimer   |    Privacy Policy   |   Browsers   |   Accessibility