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Gamma-butyrobetaine dioxygenase (also known as BBOX, GBBH or γ-butyrobetaine hydroxylase) is an enzyme that in humans is encoded by the ''BBOX1'' gene.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=8424 )〕 Gamma-butyrobetaine dioxygenase catalyses the formation of L-carnitine from gamma-butyrobetaine, the last step in the L-carnitine biosynthesis pathway. Carnitine is essential for the transport of activated fatty acids across the mitochondrial membrane during mitochondrial beta oxidation.〔 In humans, gamma-butyrobetaine dioxygenase can be found in kidney (high), liver (moderate), and brain (very low).〔 ''BBOX1'' has recently been identified as a potential cancer gene on the basis of a large-scale microarray data analysis. ==Reaction== The following reaction is catalyzed by gamma-butyrobetaine dioxygenase: :4-trimethylammoniobutanoate (γ-butyrobetaine) + 2-oxoglutarate + O2 3-hydroxy-4-trimethylammoniobutanoate (L-carnitine) + succinate + CO2 The three substrates of this enzyme are 4-trimethylammoniobutanoate (γ-butyrobetaine), 2-oxoglutarate, and O2, whereas its three products are 3-hydroxy-4-trimethylammoniobutanoate (L-carnitine), succinate, and carbon dioxide. This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with 2-oxoglutarate as one donor, and incorporation of one atom of oxygen into each donor. This enzyme participates in lysine degradation. Iron is a cofactor for gamma-butyrobetaine dioxygenase. Similar to many other 2OG oxygenases, the activity of gamma-butyrobetaine dioxygenase can be stimulated by reducing agents such as ascorbate and glutathione. The catalytic activity of gamma-butyrobetaine dioxygenase can be stimulated with different metal ions, especially potassium ions. Both the ''apo'' (PDB id: 3N6W)〔;〕 and the ''holo'' (PDB id: 3O2G)〔; 〕 structures of gamma-butyrobetaine dioxygenase have been solved, demonstrating an induced fit mechanism may contribute to the catalytic activity of gamma-butyrobetaine dioxygenase. Gamma-butyrobetaine dioxygenase is promiscus in substrate selectivity and it processes a number of modified substrates, including the natural catalytic products L-carnitine and D-carnitine, forming 3-dehydrocarnitine and trimethylaminoacetone.〔 Gamma-butyrobetaine dioxygenase also catalyses the oxidation of mildronate to form multiple products including malonic acid semialdehyde, dimethylamine, formaldehyde and (1-methylimidazolidin-4-yl)acetic acid, which is proposed to be formed via a Stevens rearrangement mechanism. Gamma-butyrobetaine dioxygenase is unique among other human 2OG oxygenases that it catalyses both hydroxylation (e.g.: L-carnitine), demethylation (e.g.: formaldehyde) and C-C bond formation (e.g.: (1-methylimidazolidin-4-yl)acetic acid). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gamma-butyrobetaine dioxygenase」の詳細全文を読む スポンサード リンク
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