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330 results on '"HISANO, T."'

70. Correlation between Structure of the Lactones and Substrate Specificity in Enzyme-Catalyzed Polymerization for the Synthesis of Polyesters

Author

Suzuki, Y., Taguchi, S., Hisano, T., Toshima, K., Matsumura, S., and Doi, Y.

Abstract

Small-size (4-membered) and medium-size (5-, 6-, and 7-membered) unsubstituted lactones as well as unsubstituted macrolides (12 and 13 membered) were subjected to the ring-opening polymerization using the extracellular PHB depolymerase from Alcaligenes faecalis T1 (PhaZAfa). The characteristic reactivities of the lactones were discussed based on a tertiary structure model of the active site of the PhaZAfa. With respect to the ring-size of the lactones, the 4-membered β-propiolactone and 6-membered δ-valerolactone (δ-VL) showed the highest polymerization activity, and δ-VL seemed to be the upper size limit for the molecular recognition of the narrow active site cleft of PhaZAfa. On the other hand, ε-caprolactone, 11-undecanolide, and 12-dodecanolide, which showed excellent polymerization activities by lipases, were scarcely polymerized by PhaZAfa. This was ascribed to the difference in the recognition sites between PhaZAfa and lipase. In addition, the effect of the substrate-binding domain of PhaZAfa and the enantioselective ring-opening polymerization of (R,S)-β-butyrolactone ((R,S)-β-BL) were studied. The substrate-binding domain lacking PhaZAfa showed higher reactivities than PhaZAfa for the polymerization of the lactones and that a significant enantioselectivity was observed at the early stage of the polymerization of (R,S)-β-BL to produce the (R)-enriched optically active poly(3-hydroxybutyrate).

Published
2003

72. Plasma Insulin-like Activity after Glucose Loading in Normals and Diabetics

Author

T Koide, Kozo Yamada, K Aoyama, and Hisano T

Subjects
medicine.medical_specialty, Glucose tolerance test, Glucose loading, medicine.diagnostic_test, business.industry, Insulin, medicine.medical_treatment, Blood sugar, medicine.disease, Obesity, Endocrinology, Internal medicine, Diabetes mellitus, medicine, Plasma insulin, business
Published
1964
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73. Crystal structures of reaction intermediates of L-2-haloacid dehalogenase and implications for the reaction mechanism.

Author

Li, Y F, Hata, Y, Fujii, T, Hisano, T, Nishihara, M, Kurihara, T, and Esaki, N

Abstract

Crystal structures of L-2-haloacid dehalogenase from Pseudomonas sp. YL complexed with monochloroacetate, L-2-chlorobutyrate, L-2-chloro-3-methylbutyrate, or L-2-chloro-4-methylvalerate were determined at 1.83-, 2.0-, 2.2-, and 2.2-A resolutions, respectively, using the complex crystals prepared with the S175A mutant, which are isomorphous with those of the wild-type enzyme. These structures exhibit unique structural features that correspond to those of the reaction intermediates. In each case, the nucleophile Asp-10 is esterified with the dechlorinated moiety of the substrate. The substrate moieties in all but the monochloroacetate intermediate have a D-configuration at the C2 atom. The overall polypeptide fold of each of the intermediates is similar to that of the wild-type enzyme. However, it is clear that the Asp-10-Ser-20 region moves to the active site in all of the intermediates, and the Tyr-91-Asp-102 and Leu-117-Arg-135 regions make conformational changes in all but the monochloroacetate intermediates. Ser-118 is located near the carboxyl group of the substrate moiety; this residue probably serves as a binding residue for the substrate carboxyl group. The hydrophobic pocket, which is primarily composed of the Tyr-12, Gln-42, Leu-45, Phe-60, Lys-151, Asn-177, and Trp-179 side chains, exists around the alkyl group of the substrate moiety. This pocket may play an important role in stabilizing the alkyl group of the substrate moiety through hydrophobic interactions, and may also play a role in determining the stereospecificity of the enzyme. Moreover, a water molecule, which is absent in the substrate-free enzyme, is present in the vicinities of the carboxyl carbon of Asp-10 and the side chains of Asp-180, Asn-177, and Ala-175 in each intermediate. This water molecule may hydrolyze the ester intermediate and its substrate. These findings crystallographically demonstrate that the enzyme reaction proceeds through the formation of an ester intermediate with the enzyme's nucleophile Asp-10.

Published
1998

92. ChemInform Abstract: REACTION OF AROMATIC N‐OXIDES WITH DIPOLAROPHILES. III. CYCLOADDITIONS OF SUBSTITUTED PHENYL ISOCYANATES TO 3,5‐DIMETHYL AND 3,5‐DIBROMOPYRIDINE N‐OXIDES AND X‐RAY CRYSTAL STRUCTURES OF THE ISOMERIC CYCLOADDUCTS

Author

HISANO, T., primary, ICHIKAWA, M., additional, MATSUOKA, T., additional, HAGIWARA, H., additional, MURAOKA, K., additional, KOMORI, T., additional, HARANO, K., additional, IDA, Y., additional, and CHRISTENSEN, A. T., additional

Published
1980
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