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Acetyl-CoA acetyltransferase, mitochondrial also known as acetoacetyl-CoA thiolase, is an enzyme that in humans is encoded by the ''ACAT1'' (Acetyl-Coenzyme A acetyltransferase 1) gene.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=38 )〕 Acetyl-Coenzyme A acetyltransferase 1 is an acetyl-CoA C-acetyltransferase enzyme. ==Structure== The gene spans approx. 27 kb and contains twelve exons interrupted by eleven introns. The region flanking the 5’ end of the gene lacks a TATA box, but contains many GC’s and also has two CAAT boxes. The gene also may have a binding site for the transcription factor, Sp1, and sequences resembling the binding sites of several other transcription factors. Additionally, there is a 101-bp DNA fragment immediately upstream from the cap site that has promoter activity. The human ACAT1 gene produces a chimeric mRNA through trans-splicing, a process in which separate transcripts from chromosomes 1 and 7 are spliced together. The chimeric mRNA transcript uses two sections to initiate translation: AUG(1397-1399) and GGC(1274-1276). Initiation of the first codon (AUG) results in the translation of a 50-kDa ACAT1, and initiation of the other (GGC) produces another enzymatically active 56-kDa isoform respectively; the 56kDa isoform is naturally present in human cells, including human monocyte-derived macrophages. The resulting transcript encodes ACAT1, which is a 45.1 kDa protein composed of 427 amino acids.〔]〕〔(【引用サイトリンク】 work = Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) )〕 It is also is a homotetrameric protein that has nine transmembrane domains (TMDs). One active residue is a Histidine at the 460th position, which is in the 7th TMD. ACAT1 has seven free Cysteine residues, but they do not affect catalytic activity. There are two functional sections of this protein, TMD7 and TMD8; one side is involved in substrate binding and catalysis, while the other is involved in subunit interactions and binding. 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「ACAT1」の詳細全文を読む スポンサード リンク
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