Molecular cloning of the human and murine 2-amino-3-ketobutyrate coenzyme A ligase cDNAs
Molecular cloning of the human and murine 2-amino-3-ketobutyrate coenzyme A ligase cDNAs
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DOI：
10.1046/j.1432-1327.2000.01175.x
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发表时间：
2000-03-01
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影响因子：
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通讯作者：
Polak, JM
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文献类型：
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作者：
Edgar, AJ;Polak, JM
在原核生物和真核生物中，L苏氨酸脱氢酶(EC1.1.1103)和2-氨基-3-酮丁酸辅酶A连接酶(KBL；EC2.3.1.29)通过两步生化途径将L苏氨酸转化为甘氨酸。编码这些酶的基因在原核生物中已被描述，但在真核生物中尚未被描述。我们报道了该途径中的第二种酶KBL的转录本的克隆，以及人和小鼠肺的转录本和牛肝的部分转录本。从纯化的牛KBL蛋白中得到两个肽序列，一个来自N-末端，另一个来自含有吡哆醛5‘-磷酸结合赖氨酸残基的肽[Tom，H.&Davis，L.(1994)J.Biol]。化学。269,4057-4064]，与从牛肝获得的转录本的概念翻译区域相同。牛肝脏的部分转录本与人类转录本非常相似，在核苷酸和氨基酸水平上分别有91%和92%的同源性。人和小鼠的KBL转录本长1.5kb，ORF分别编码419和416个残基的蛋白质。小鼠蛋白与人类蛋白有90%的同源性。与肺相比，人类转录产物在心脏、脑、肝脏和胰腺中表达强烈。人和小鼠蛋白的N末端都具有线粒体输入序列的特征。人和鼠的蛋白都与来自大肠杆菌的具有良好特性的原核生物KLb蛋白有54%的同源性。通过对人类DNA序列的数据库搜索，我们在22q12-13号染色体上发现了人类KBL基因，该基因由9个外显子组成，在IV号染色体上发现了一个假想的秀丽线虫KLB基因，该基因由5个外显子组成，长度超过2 kb。
The conversion of l-threonine to glycine in both prokaryotes and eukaryotes takes place through a two-step biochemical pathway involving the enzymes l-threonine dehydrogenase (EC 1.1.1103) and 2-amino-3-ketobutyrate coenzyme A ligase (KBL; EC 2.3.1.29). The genes encoding these enzymes have been described in prokaryotes but not in eukaryotes. We report the cloning of transcripts for KBL, the second enzyme in the pathway, from human and murine lung and a partial transcript from bovine liver. Two peptide sequences from the purified bovine KBL protein, one from the N-terminus and the other from the peptide containing the pyridoxal 5'-phosphate-binding lysine residue [Tong, H. & Davis, L. (1994) J. Biol. Chem. 269, 4057-4064], are identical with regions of the conceptual translation of the transcript obtained from bovine liver. The partial transcript from bovine liver was very similar to the human transcript, being 91% and 92% identical at the nucleotide and amino-acid levels, respectively. The human and murine KBL transcripts are 1.5 kb long, with ORFs encoding proteins of 419 and 416 residues, respectively. The mouse protein has 90% identity with the human protein. The human transcript is strongly expressed in heart, brain, liver and pancreas compared with the lung. The N-termini of both human and mouse proteins have characteristics of mitochondrial import sequences. Both human and murine proteins have 54% identity with the well-characterised prokaryote KLB protein from Escherichia coli. Database searches with the human cDNA sequence enabled us to identify the human KBL gene on chromosome 22q12-13, consisting of nine exons over 9 kb, and a hypothetical Caenorhabditis elegans KLB gene on chromosome IV, consisting of five exons over 2 kb.