Methylcobalamin/ja

Methylcobalamin/ja

Clinical data
Trade names	Cobolmin
AHFS/Drugs.com	International Drug Names
Routes of administration	口から, 舌下, 注射
ATC code	B03BA05 (WHO)
Legal status
Legal status	US: OTC
Pharmacokinetic data
Excretion
Identifiers
IUPAC name carbanide; cobalt(3+);
CAS Number	13422-55-4 Y
PubChem CID	6436232
ChemSpider	29368587
UNII	BR1SN1JS2W
ChEMBL	ChEMBL1697757 N
Chemical and physical data
Formula	C63H91CoN13O14P
Molar mass	1344.405 g·mol−1
3D model (JSmol)	Interactive image
SMILES [CH3-].CC1=CC2=C(C=C1C)N(C=N2)C3C(C(C(O3)CO)OP(=O)([O-])OC(C)CNC(=O)CCC4(C(C5C6(C(C(C(=N6)C(=C7C(C(C(=N7)C=C8C(C(C(=N8)C(=C4[N-]5)C)CCC(=O)N)(C)C)CCC(=O)N)(C)CC(=O)N)C)CCC(=O)N)(C)CC(=O)N)C)CC(=O)N)C)O.[Co+3]
InChI InChI=1S/C62H90N13O14P.CH3.Co/c1-29-20-39-40(21-30(29)2)75(28-70-39)57-52(84)53(41(27-76)87-57)89-90(85,86)88-31(3)26-69-49(83)18-19-59(8)37(22-46(66)80)56-62(11)61(10,25-48(68)82)36(14-17-45(65)79)51(74-62)33(5)55-60(9,24-47(67)81)34(12-15-43(63)77)38(71-55)23-42-58(6,7)35(13-16-44(64)78)50(72-42)32(4)54(59)73-56;;/h20-21,23,28,31,34-37,41,52-53,56-57,76,84H,12-19,22,24-27H2,1-11H3,(H15,63,64,65,66,67,68,69,71,72,73,74,77,78,79,80,81,82,83,85,86);1H3;/q;-1;+3/p-2 Key:ZFLASALABLFSNM-UHFFFAOYSA-L
NY (what is this?)  (verify)

メチルコバラミン（Methylcobalamin, メコバラミン、MeCbl、MeB₁₂）は、[[Vitamin B12|ビタミンB₁₂]の一種であるコバラミンである。］ コバルトのシアノ基がメチル基に置換されている点でシアノコバラミンとは異なる。メチルコバラミンは八面体のコバルト(III)中心を持ち、明るい赤色の結晶として得られる。 配位化学の観点からは、メチルコバラミンが金属-アルキル結合を含む化合物の珍しい例として注目される。ニッケル-メチル中間体は、メタン生成の最終段階として提案されている。

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

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

Methylcobalamin that is ingested is not used directly as a cofactor, but is first converted by MMACHC into cob(II)alamin. Cob(II)alamin is then later converted into the other two forms, adenosylcobalamin and methylcobalamin for use as cofactors. That is, methylcobalamin is first dealkylated and then regenerated.

According to one author, it is important to treat vitamin B₁₂ deficiency with hydroxocobalamin or cyanocobalamin or a combination of adenosylcobalamin and methylcobalamin, and not methylcobalamin alone.

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.

Functions

This vitamer, along with adenosylcobalamin, 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.

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.

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

A lack of cobalamin can lead to megaloblastic anemia and subacute combined degeneration of the spinal cord.

こちらも参照

• Cobamamide/ja
• シアノコバラミン
• ヒドロキソコバラミン
• ビタミンB12
• Cobalamin biosynthesis/ja