VITAMINS

Physiological roles of the Nudix hydrolase family in the metabolism of vitamin-derived coenzymes in plants

Takahisa Ogawa

2018 Volume 92 Issue 2 Pages 53-62
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_53

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The Nudix (Nucleoside diphosphate linked to some other moiety X) hydrolases, NUDXs, are the protein family that hydrolyzes a wide variety of nucleoside diphosphate derivatives including canonical and oxidized nucleoside di- and triphosphates, nucleotide-sugars, and several coenzymes such as NAD(P) H, FAD, and CoA which are derived from niacin, Àavin, and pantothenic acid, respectively. Arabidopsis thaliana possesses 28 NUDX genes (AtNUDX1-27 and DCP2) divided into three types, i.e., cytosolic, chloroplastic, and mitochondrial types, based on their subcellular localization. There is increasing evidence that AtNUDXs play physiological roles in the regulation of the levels of various metabolic intermediates and stress responses. Recently, we have reported that the regulation of intracellular levels of GDP-D-mannose, a metabolic intermediate of ascorbate biosynthesis, by cytosolic AtNUDX9 is involved in the response of plants to NH₄⁺ and that the modulation of the cellular levels and redox state of pyridine nucleotides including NADPH by chloroplastic AtNUDX19 participates in the responses of plants to photooxidative stress and hormones. Furthermore, we have demonstrated that the regulation of cellular NADH levels by both cytosolic AtNUDX6 and 7 contributes to the modulation of the poly(ADP-ribosyl)ation reaction which is associated with the post-translational modi¿cation of proteins in biotic/abiotic stress responses, although the existence of AtNUDX6 and 7 themselves or other interacting factors is important for the control of salicylic acid signaling pathway. These findings suggest that NUDXs play important roles in various cellular responses through degradation of vitamin-derived coenzymes and their intermediates.

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Study on Mechanism Underlying Metabolic Biotransformation of Vitamin K

Yoshihisa Hirota

2018 Volume 92 Issue 2 Pages 63-72
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_63

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The vitamin K family comprises vitamin K₁(phylloquinone [PK]) derived from plants, vitamin K₂ (menaquinone-n [MK-n]) from intestinal bacteria, and vitamin K₃ (menadione [MD]) derived synthetically without a bioactive side chain. Diet-derived vitamin K mainly comprises PK but menaquinone-4 (MK4) is predominantly found in tissues. It has been predicted that PK undergoes a transformation to MK-4 in tissues, resulting in MK-4 accumulation within the tissues. However, the mechanism underlying this biotransformation has remained unknown for more than 60 years. Hence, we aimed to elucidate the mechanism underlaying the metabolic biotransformation of vitamin K. 　Diet-derived vitamin K is partly absorbed by the lymphatic vessels in small intestinal villi, i.e., lacteals, and most of it is metabolized to MD by a side-chain cleavage enzyme in the small intestine, although this enzyme has been thought to be present in the tissue. The MD thus transformed from vitamin K is transported from the lymphatic vessels to all tissues via systemic circulation. We previously reported that MD is transformed to MK-4 by UbiA prenyltransferase domain containing protein 1 (UBIAD1) present in each tissue. The MK-4 thus transformed from MD acts as a biologically active vitamin K and exerts various physiological functions such as blood coagulation and bone formation via vitamin K-dependent gamma-carboxylase (GGCX), steroid and xenobiotic receptor (SXR), and protein kinase A (PKA) signaling. Therefore, we have proposed that MK-4 is no longer within a vitamin framework and that it has physiologically and nutritionally important hormone-like functions. Thus, we have successfully elucidated a part of the mechanism undelaying the metabolic biotransformation of vitamin K.

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An attempt to determine vitamin B₁₂requirement based on the disease risk reduction

Application of determination method used for the vitamin D requirement

Kiyoshi Tanaka, Misora Ao, Akiko Kuwabara

2018 Volume 92 Issue 2 Pages 73-78
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_73

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Vitamin deficiency causes classical deficiency diseases. Vitamin insufficiency is milder than vitamin deficiency but it increases the risk of non-communicable diseases (NCDs). Considering the importance of NCDs in Japan, vitamin requirement must be determined based on the risk reduction of NCDs. In Dietary Reference Intakes (DRIs) for Japanese 2015, vitamin B₁₂requirement was determined based on the treatment outcome of anemia in patients with pernicious anemia, a vitamin B₁₂deficiency disease, after intra-muscular injection of vitamin B₁₂. However, there are various problems in this determination of vitamin B₁₂requirement in DRIs for Japanese 2015. One of the problems is that the number of subjects is extremely small (N=7).
Therefore, we attempted to propose a novel method to determine vitamin B₁₂requirement based on the risk reduction of diseases. In the determination of vitamin B₁₂requirement by this method, the risk of osteoporotic fracture due to vitamin D insufficiency was taNen into consideration. It was thought that vitamin D requirement determined by DRI in USA/Canada 2011 could be of use as a reference because the vitamin D requirement was determined by taking the risk of osteoporotic fracture due to vitamin D insufficiency into consideration. Vitamin B₁₂or folate insufficiency causes hyperhomocysteinemia which is the risk factor of cardiovascular diseases and osteoporotic fracture. Our recent analysis of cohort studies led to the following findings: plasma homocysteine (Hcy) concentration made a good prediction for the risN of osteoporotic fracture and cardiovascular events. The cut-off value of plasma Hcy concentration to avoid such risks was less than 10 nmol/mL. This cut-off value of plasma Hcy concentration was lower than that cited in DRIs for Japanese 2015 (14 nmol/mL). To avoid this insufficiency, vitamin B₁₂ requirement was much higher than that considered for a long time.
In conclusion, we have proposed a novel method to determine vitamin B₁₂requirement based on the risk reduction of diseases. The application of this method to the decision of DRIs in the future could be awaited.

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Metal-ion-independent oxygenation reactions

Hideyuki Hayashi

2018 Volume 92 Issue 2 Pages 79-83
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_79

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Bovine milk as a vitamin B₁₂source

Fumio Watanabe

2018 Volume 92 Issue 2 Pages 84-85
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_84

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GabR: Bacterial transcriptional regulator depending on pyridoxal 5’-phophate

Tohru Yoshimura

2018 Volume 92 Issue 2 Pages 86-89
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_86

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[title in Japanese]

Hideaki Tsuge

2018 Volume 92 Issue 2 Pages 90
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_90

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...

2018 Volume 92 Issue 2 Pages 91-92
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_91

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[title in Japanese]

Hisaaki Mihara, [in Japanese], Yasushi Tani, [in Japanese], Ryuuta Tob ...

2018 Volume 92 Issue 2 Pages 92
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_92

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[title in Japanese]

[in Japanese], Kiyoshi Fukui

2018 Volume 92 Issue 2 Pages 93
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_93

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[title in Japanese]

[in Japanese]

2018 Volume 92 Issue 2 Pages 94
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_94

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[title in Japanese]

Tatsuo Kurihara

2018 Volume 92 Issue 2 Pages 94-95
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_94_2

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[title in Japanese]

Yoko Nitta

2018 Volume 92 Issue 2 Pages 95-96
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_95

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[title in Japanese]

Katsushi Koyama

2018 Volume 92 Issue 2 Pages 96-98
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_96

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[title in Japanese]

Nobuaki Wakamatsu, kenichiro Yamada, [in Japanese]

2018 Volume 92 Issue 2 Pages 98
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_98

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[title in Japanese]

Kaduki Okamoto

2018 Volume 92 Issue 2 Pages 99-100
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_99

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[title in Japanese]

Noe Kawade, [in Japanese], [in Japanese], Misato Kobayashi, Fumihiko H ...

2018 Volume 92 Issue 2 Pages 101-102
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_101

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[title in Japanese]

Keisuke Sakiyama, Takahiro Ishikawa

2018 Volume 92 Issue 2 Pages 102
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_102

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[title in Japanese]

Shosuke Kojo

2018 Volume 92 Issue 2 Pages 102-103
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_102_2

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JOURNAL OF NUTRITIONAL SCIENCE AND VITAMINOLOGY　Vol 63, No 6（December, 2017）

2018 Volume 92 Issue 2 Pages 104-108
Published: February 25, 2018
Released on J-STAGE: February 28, 2019

DOIhttps://doi.org/10.20632/vso.92.2_104

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