著者

Keiko KOBAYASHI Yuki ISHIZAKI Shosuke KOJO Hiroe KIKUZAKI

出版者

Center for Academic Publications Japan

雑誌

Journal of Nutritional Science and Vitaminology (ISSN:03014800)

巻号頁・発行日

vol.62, no.2, pp.123-129, 2016 (Released:2016-06-03)

参考文献数

30

被引用文献数

3 6

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Sphingomyelinases (SMases) are key enzymes involved in many diseases which are caused by oxidative stress, such as atherosclerosis, diabetes mellitus, nonalcoholic fatty liver disease, and Alzheimer’s disease. SMases hydrolyze sphingomyelin to generate ceramide, a well-known pro-apoptotic lipid. SMases are classified into five types based on pH optimum, subcellular localization, and cation dependence. Previously, we demonstrated that elevation of secretory sphingomyelinase (sSMase) activity increased the plasma ceramide concentration under oxidative stress induced by diabetes and atherosclerosis in murine models. These results suggest that sSMase inhibitors can prevent the progress of these diseases. The present study demonstrated that sSMase activity was activated by oxidation and inhibited by reduction. Furthermore, we examined whether catechins inhibited the sSMase activity in a physiological plasma concentration. Among catechins, (−)-epicatechin 3-O-gallate (ECg) exhibited strong inhibitory effect on sSMase (IC50=25.7 μM). This effect was attenuated by methylation at the 3″- or 4″-position. On the other hand, (−)-epigallocatechin 3-O-gallate (EGCg) and (−)-catechin 3-O-gallate (Cg) exhibited weaker inhibitory activity than ECg, and (−)-epicatechin and (−)-epigallocatechin did not affect sSMase activity. Additionally, one synthetic catechin, (−)-3′-O-methylepigallocatechin 3-O-gallate (EGCg-3′-O-Me), showed the strongest inhibitory effect (IC50=1.7 μM) on sSMase. This phenomenon was not observed for (−)-4′-O-methylepigallocatechin 3-O-gallate. These results suggest that the reduction potential, the presence of the galloyl residue at the C-3 position, and the steric requirement to interact with sSMase protein are important for effective inhibition of sSMase.

著者

Kyoko Yamane Tomoe Yamada-Kato Natsuko Haga Kaori Ishida Seiji Murayama Keiko Kobayashi Isao Okunishi

出版者

Japanese Society of Breeding

雑誌

Breeding Science (ISSN:13447610)

巻号頁・発行日

vol.73, no.3, pp.237-245, 2023 (Released:2023-07-27)

参考文献数

46

被引用文献数

1

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Wasabi (Japanese horseradish, Eutrema japonicum) is the only cultivated species in the genus Eutrema with functional components that provide a strong pungent flavor. To evaluate genetic resources for wasabi breeding, we surveyed variations in the two most abundant isothiocyanate (ITC) components in wasabi, allyl isothiocyanate (AITC) and 6-methylsulfinyl (hexyl) isothiocyanate (6-MSITC, hexaraphane). We also examined the phylogenetic relationships among 36 accessions of wild and cultivated wasabi in Japan using chloroplast DNA analysis. Our results showed that (i) the 6-MSITC content in currently cultivated wasabi accessions was significantly higher than in escaped cultivars, whereas the AITC content was not significantly different. (ii) Additionally, the 6-MSITC content in cultivated wasabi was significantly lower in the spring than during other seasons. This result suggested that the 6-MSITC content responds to environmental conditions. (iii) The phylogenetic position and the 6-MSITC content of accessions from Rebun, Hokkaido Prefecture had different profiles compared with those from southern Honshu, Japan, indicating heterogeneity of the Rebun populations from other Japanese wasabi accessions. (iv) The total content of AITC and 6-MSITC in cultivated wasabi was significantly higher than that of wild wasabi. In conclusion, old cultivars or landraces of wasabi, “zairai”, are the most suitable candidates for immediate use as genetic resources.

著者

Keiko Kobayashi Kae Akita Masashi Suzuki Daisaku Ohta Noriko Nagata

出版者

Japanese Society for Plant Biotechnology

雑誌

Plant Biotechnology (ISSN:13424580)

巻号頁・発行日

vol.38, no.1, pp.109-116, 2021-03-25 (Released:2021-03-25)

参考文献数

35

被引用文献数

4

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The exine acts as a protectant of the pollen from environmental stresses, and the pollen coat plays an important role in the attachment and recognition of the pollen to the stigma. The pollen coat is made of lipidic organelles in the tapetum. The pollen coat is necessary for fertility, as pollen coat-less mutants, such as those deficient in sterol biosynthesis, show severe male sterility. In contrast, the exine is made of sporopollenin precursors that are biosynthesized in the tapetum. Some mutants involved in sporopollenin biosynthesis lose the exine but show the fertile phenotype. One of these mutants, cyp704b1, was reported to lose not only the exine but also the pollen coat. To identify the cause of the fertile phenotype of the cyp704b1 mutant, the detailed structures of the tapetum tissue and pollen surface in the mutant were analyzed. As a result, the cyp704b1 mutant completely lost the normal exine but had high-electron-density granules localized where the exine should be present. Furthermore, normal lipidic organelles in the tapetum and pollen coat embedded between high-electron-density granules on the pollen surface were observed, unlike in a previous report, and the pollen coat was attached to the stigma. Therefore, the pollen coat is necessary for fertility, and the structure that functions like the exine, such as high-electron-density granules, on the pollen surface may play important roles in retaining the pollen coat in the cyp704b1 mutant.