Improvement of dye-mediated dehydrogenase activity of pyranose oxidase by site-directed mutagenesis

　Pyranose oxidase (EC 1.1.3.10 ; PROD) catalyzes the oxidation of aldopyranoses at the position C‒2 to yield the corresponding 2‒keto-aldoses and H2O2 , using oxygen as an electron acceptor. The enzyme shows broad substrate specificity as well as reactivity for 1,5‒anhydro‒d‒glucitol (1,5‒AG), which is known as a clinical glycemic marker. It is considered that the reactivity of PROD for 1,5‒AG is useful in the development of an amperometric-type biosensor, which is a convenient diagnostic device for selfmonitoring blood glucose (SMBG). However, the levels of dissolved oxygen in blood affect biosensor systems that are equipped with an artificial electron mediator. In the present study, we attempted to develop an O2‒insensitive oxidase that would improve the dye-mediated dehydrogenase activity. We performed site-directed mutagenesis on PROD isolated from basidiomycetous fungus No. 52, which generated 11 mutants. The amino acid substitution Q421A exhibited a significant decrease (8.8% of wild type) in its oxidase activity, whereas it maintained its dehydrogenase activity (67% of wild type). In this study, we characterized PROD mutants from basidiomycetous fungus No. 52, which showed improved dye-mediated dehydrogenase activity

Free fatty acid receptors, G protein-coupled receptor 120 and G protein-coupled receptor 40, are essential for oil-induced gastric inhibitory polypeptide secretion

Aims/Introduction: Incretin hormone glucose‐dependent insulinotropic polypeptide/gastric inhibitory polypeptide (GIP) plays a key role in high‐fat diet‐induced obesity and insulin resistance. GIP is strongly secreted from enteroendocrine K cells by oil ingestion. G protein‐coupled receptor (GPR)120 and GPR40 are two major receptors for long chain fatty acids, and are expressed in enteroendocrine K cells. In the present study, we investigated the effect of the two receptors on oil‐induced GIP secretion using GPR120‐ and GPR40‐double knockout (DKO) mice. Materials and Methods: Global knockout mice of GPR120 and GPR40 were crossbred to generate DKO mice. Oral glucose tolerance test and oral corn oil tolerance test were carried out. For analysis of the number of K cells and gene expression in K cells, DKO mice were crossbred with GIP‐green fluorescent protein knock‐in mice in which visualization and isolation of K cells can be achieved. Results: Double knockout mice showed normal glucose‐induced GIP secretion, but no GIP secretion by oil. We then investigated the number of K cells and gene characteristics in K cells isolated from GIP‐green fluorescent protein knock‐in mice. Deficiency of both receptors did not affect the number of K cells in the small intestine or expression of GIP messenger ribonucleic acid in K cells. Furthermore, there was no significant difference in the expression of the genes associated with lipid absorption or GIP secretion in K cells between wild‐type and DKO mice. Conclusions: Oil‐induced GIP secretion is triggered by the two major fatty acid receptors, GPR120 and GPR40, without changing K‐cell number or K‐cell characteristics

Animal-borne video systems provide insight into the reproductive behavior of the Asian black bear

Previous studies on the mating system of the Asian black bear (Ursus thibetanus) have been limited to observations of captive populations and estimations of multiple paternities. Hence, the mating system of wild bears remains poorly understood. Animal-borne camera systems (i.e., cameras mounted on animals) provide novel tools to study the behavior of elusive animals. Here, we used an animal-borne video system to record the activities of wild bears during the mating season. Video camera collars were attached to four adult Asian black bears (male “A” and “B,” and female “A” and “B”) captured in Tokyo, central Japan, in May and June 2018. The collars were retrieved in July 2018, after which the video data were downloaded and analyzed in terms of bear activity and mating behavior. All the bears were found to interact with other uniquely identifiable bears for some of the time (range 9–22 days) during the deployment period (range 36–45 days), and multiple mating in males was documented. Both males and females exhibited different behaviors on social days (i.e., days when the bear interacted with conspecifics) compared with solitary days (i.e., days with no observed interactions with conspecifics). Compared with solitary days, the bears spent a lower proportion of time on foraging activities and higher proportion of time on resting activities on social days. Our results suggest that Asian black bears have a polygamous mating system, as both sexes consort and potentially mate with multiple partners during a given mating season. Furthermore, bears appeared to reduce their foraging activities on social days and engaged more in social interactions.publishedVersio