Voilley N, Roduit R, Vicaretti R, Bonny C, Waeber G, Dyck J R, Lopaschuk G D, Prentki M
Molecular Nutrition Unit, Department of Nutrition, University of Montreal and the CR Centre Hospitalier de l'Université de Montréal and Institut du Cancer, 1560 Sherbrooke Est, Montreal, Quebec H2L 4M1, Canada.
Biochem J. 1999 May 15;340 ( Pt 1)(Pt 1):213-7.
To gain insight into the function and regulation of malonyl-CoA decarboxylase (MCD) we have cloned rat MCD cDNA from a differentiated insulin-secreting pancreatic beta-cell-line cDNA library. The full-length cDNA sequence shows 69% identity with the cDNA cloned previously from the goose uropygial gland, and predicts a 492 amino acid protein of 54.7 kDa. The open reading frame contains an N-terminal mitochondrial targeting sequence and the C-terminal part of the enzyme ends with a peroxisomal (Ser-Lys-Leu) targeting motif. Since the sequence does not reveal hydrophobic domains, MCD is most likely expressed in the mitochondrial matrix and inside the peroxisomes. A second methionine residue, located 3' of the mitochondrial presequence, might be the first amino acid of a putative cytosolic MCD, since the nucleotide sequence around it fits fairly well with a consensus Kozak site for translation initiation. However, primer extension detects the presence of only one transcript initiating upstream of the first ATG, indicating that the major, if not exclusive, transcript expressed in the pancreatic beta-cell encodes MCD with its mitochondrial presequence. The sequence also shows multiple possible sites of phosphorylation by casein kinase II and protein kinase C. mRNA tissue-distribution analysis indicates a transcript of 2.2 kb, and that the MCD gene is expressed over a wide range of rat tissues. The distribution of the enzyme shows a broad range of activities from very low in the brain to elevated in the liver and heart. The results provide the foundations for further studies of the role of MCD in lipid metabolism and metabolic signalling in various tissues.
为深入了解丙二酰辅酶A脱羧酶（MCD）的功能和调节机制，我们从一个分化的胰岛素分泌胰腺β细胞系cDNA文库中克隆了大鼠MCD cDNA。全长cDNA序列与先前从鹅尾脂腺克隆的cDNA有69%的同源性，并预测编码一个由492个氨基酸组成、分子量为54.7 kDa的蛋白质。开放阅读框包含一个N端线粒体靶向序列，该酶的C端部分以过氧化物酶体靶向基序（Ser-Lys-Leu）结尾。由于该序列未显示疏水结构域，MCD很可能在线粒体基质和过氧化物酶体内表达。位于线粒体前序列3'端的第二个甲硫氨酸残基可能是假定的胞质MCD的第一个氨基酸，因为其周围的核苷酸序列与翻译起始的共有Kozak位点相当吻合。然而，引物延伸检测到仅在第一个ATG上游起始的一个转录本的存在，这表明在胰腺β细胞中表达的主要（如果不是唯一）转录本编码带有线粒体前序列的MCD。该序列还显示了多个可能被酪蛋白激酶II和蛋白激酶C磷酸化的位点。mRNA组织分布分析表明有一个2.2 kb的转录本，并且MCD基因在大鼠的多种组织中广泛表达。该酶的分布显示出广泛的活性范围，从大脑中的极低水平到肝脏和心脏中的升高水平。这些结果为进一步研究MCD在各种组织中的脂质代谢和代谢信号传导中的作用奠定了基础。
