関: methylcobalamin

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/11/02 12:11:44」(JST)

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Methylcobalamin (mecobalamin, MeCbl, or MeB₁₂) is a cobalamin, a form of vitamin B₁₂. It differs from cyanocobalamin in that the cyanide is replaced by a methyl group.^[1] Methylcobalamin features an octahedral cobalt(III) centre. Methylcobalamin can be obtained as bright red crystals.^[2] From the perspective of coordination chemistry, methylcobalamin is notable as a rare example of a compound that contains metal-alkyl bonds. Nickel-methyl intermediates have been proposed for the final step of methanogenesis.

Methylcobalamin is equivalent physiologically to vitamin B₁₂, and can be used to prevent or treat pathology arising from a lack of vitamin B₁₂ (vitamin B12 deficiency), such as pernicious anemia.

Methylcobalamin is also used in the treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis.

Production

Methylcobalamin physically resembles the other forms of vitamin B₁₂, occurring as dark red crystals that freely form cherry-colored transparent solutions in water.

Methylcobalamin can be produced in the laboratory by reducing cyanocobalamin with sodium borohydride in alkaline solution, followed by the addition of methyl iodide.^[2]

Functions

This vitamer is one of two active coenzymes used by vitamin B₁₂-dependent enzymes and is the specific vitamin B₁₂ form used by 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), also known as methionine synthase.^{[citation needed]}

Methylcobalamin participates in the Wood-Ljungdahl pathway, which is a pathway by which some organisms utilize carbon dioxide as their source of organic compounds. In this pathway, methylcobalamin provides the methyl group that couples to carbon monoxide (derived from CO₂) to afford acetyl-CoA. Acetyl-CoA is a derivative of acetic acid that is converted to more complex molecules as required by the organism.^[3]

Methylcobalamin is produced by some bacteria. It plays an important role in the environment. In the environment, it is responsible for the biomethylation of certain heavy metals. For example, the highly toxic methylmercury is produced by the action of methylcobalamin.^[4] In this role, methylcobalamin serves as a source of "CH₃⁺".

References

^ L. R. McDowell, Vitamins in animal and human nutrition
^ ^a ^b David Dophin. Preparation of the Reduced Forms of Vitamin B₁₂ and of Some Analogs of the Vitamin B₁₂ Coenzyme Containing a Cobalt-Carbon Bond. D.B. McCormick and L.D. Wright, Eds. 1971;Vol. XVIII:34-54.
^ Fontecilla-Camps, J. C.; Amara, P.; Cavazza, C.; Nicolet, Y.; Volbeda, A. (2009). "Structure–function relationships of anaerobic gas-processing metalloenzymes". Nature 460 (7257): 814–822. doi:10.1038/nature08299. PMID 19675641. edit
^ Zenon Schneider, Andrzej Stroiński, Comprehensive B12: Chemistry, Biochemistry, Nutrition, Ecology, Medicine

English Journal

Oral vitamin B12 replacement: an effective treatment for vitamin B12 deficiency after total gastrectomy in gastric cancer patients.

Kim HI, Hyung WJ, Song KJ, Choi SH, Kim CB, Noh SH.SourceDepartment of Surgery, Yonsei University College of Medicine, Seoul, Korea.
Annals of surgical oncology.Ann Surg Oncol.2011 Dec;18(13):3711-7. Epub 2011 May 10.
BACKGROUND: Vitamin B12 deficiency is a common long-term sequelae after total gastrectomy. Intramuscular injection of vitamin B12 is the only known treatment. We investigated the efficacy and safety of oral vitamin B12 replacement for gastric cancer patients with vitamin B12 deficiency after total g
PMID 21556950

Connection between multimetal(loid) methylation in methanoarchaea and central intermediates of methanogenesis.

Thomas F, Diaz-Bone RA, Wuerfel O, Huber B, Weidenbach K, Schmitz RA, Hensel R.SourceDepartment of Microbiology I, University of Duisburg-Essen, Campus Essen, Universitaetsstr. 2, 45141 Essen, Germany. frank.thomas@uni-due.de
Applied and environmental microbiology.Appl Environ Microbiol.2011 Dec;77(24):8669-75. Epub 2011 Oct 14.
In spite of the significant impact of biomethylation on the mobility and toxicity of metals and metalloids in the environment, little is known about the biological formation of these methylated metal(loid) compounds. While element-specific methyltransferases have been isolated for arsenic, the strik
PMID 22003009

Japanese Journal

突発性難聴難治例に対するプロスタグランディンI2製剤を用いた二次治療の検討

松田和徳,川田育二,阿部律子,北村嘉章,関根和教,阿部晃治,田村公一,武田憲昭
耳鼻咽喉科臨床 105(4), 375-379, 2012-04-01
… We then compared them with those of mecobalamin, a derivative of vitamin B12. … A significant improvement in the average hearing level was obtained in patients who received beraprost sodium for 12 weeks, but not in patients who received mecobalamin. … The hearing levels at 125 Hz, 250 Hz, 500 Hz and 8000 Hz significantly improved after the salvage treatment of beraprost sodium over those of mecobalamin. …
NAID 10030517388

急性中耳炎に随伴する内耳障害の検討

鈴木健策
耳鼻咽喉科臨床 103(11), 1003-1008, 2010-11-01
… Those with inner ear damage were treated by oral mecobalamin and adenosine triphosphate, and many had betamethasone added. …
NAID 10027449397

頸部術後に CRPS (Complex Regional Pain Syndrome) tupe I を生じた1例

矢吹健一郎,佃守,谷垣裕二,池田陽一,愛甲健,小山主夫
耳鼻咽喉科臨床 103(1), 65-69, 2010-01-01
… She was diagnosed as having CRPS with thermography and treated with glucocorticoid, mecobalamin, and nonsteroidal anti-inflammatory drugs (NSAIDs). …
NAID 10026216431

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リンク元

「メコバラミン」

Methylcobalamin
Systematic (IUPAC) name
	carbanide; cobalt(3+);
Clinical data
AHFS/Drugs.com	International Drug Names
Legal status	US: OTC;
Routes	oral,sublingual,injection.
Identifiers
CAS number	13422-55-4
ATC code	B03BA05
PubChem	CID 6436232
UNII	BR1SN1JS2W
ChEMBL	CHEMBL1697757
Chemical data
Formula	C63H91CoN13O14P
Mol. mass	1344.40 g/mol
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英: mecobalamin
商: イセコバミン、カロマイドMe、コメスゲン、コバメチン、ノイメチコール、ハイトコバミンM、バンコミン、ビーコバM、メコバマイド、メコラミン、メチクール、メチコバール、メチコバイド、ヨウコバール、レチコラン、ローミス
関: ビタミンＢ剤

GOO. 1454-1458

ビタミンB₁₂の一つ

製品

メチコバール

錠：250μg/500μg

細粒：1mg

注：500μg/1mL

薬理作用

生体内メチル基転移反応の補酵素

核酸やリン脂質の代謝

末梢性神経障害における神経の修復・再生

適応

内服：末梢性神経障害
注射：末梢性神経障害，ビタミンB₁₂欠乏による巨赤芽球性貧血

副作用

過敏症(発疹など)、
内服：消化器症状(胃部不快感，食欲不振，悪心，下痢，腹痛)
注射：注射部位の疼痛，硬結，頭痛，発汗，発熱感

重大

アナフィラキシー様反応

[1] L. R. McDowell, Vitamins in animal and human nutrition

[MechB12-2] David Dophin. Preparation of the Reduced Forms of Vitamin B₁₂ and of Some Analogs of the Vitamin B₁₂ Coenzyme Containing a Cobalt-Carbon Bond. D.B. McCormick and L.D. Wright, Eds. 1971;Vol. XVIII:34-54.

[3] Fontecilla-Camps, J. C.; Amara, P.; Cavazza, C.; Nicolet, Y.; Volbeda, A. (2009). "Structure–function relationships of anaerobic gas-processing metalloenzymes". Nature 460 (7257): 814–822. doi:10.1038/nature08299. PMID 19675641. edit

[4] Zenon Schneider, Andrzej Stroiński, Comprehensive B12: Chemistry, Biochemistry, Nutrition, Ecology, Medicine

匿名

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案内

mecobalamin