Calder R B, Williams R S, Ramaswamy G, Rock C O, Campbell E, Unkles S E, Kinghorn J R, Jackowski S
Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
J Biol Chem. 1999 Jan 22;274(4):2014-20. doi: 10.1074/jbc.274.4.2014.
Pantothenate kinase (PanK) is the key regulatory enzyme in the CoA biosynthetic pathway. The PanK gene from Escherichia coli (coaA) has been previously cloned and the enzyme biochemically characterized; highly related genes exist in other prokaryotes. We isolated a PanK cDNA clone from the eukaryotic fungus Aspergillus nidulans by functional complementation of a temperature-sensitive E. coli PanK mutant. The cDNA clone allowed the isolation of the genomic clone and the characterization of the A. nidulans gene designated panK. The panK gene is located on chromosome 3 (linkage group III), is interrupted by three small introns, and is expressed constitutively. The amino acid sequence of A. nidulans PanK (aPanK) predicted a subunit size of 46.9 kDa and bore little resemblance to its bacterial counterpart, whereas a highly related protein was detected in the genome of Saccharomyces cerevisiae. In contrast to E. coli PanK (bPanK), which is regulated by CoA and to a lesser extent by its thioesters, aPanK activity was selectively and potently inhibited by acetyl-CoA. Acetyl-CoA inhibition of aPanK was competitive with respect to ATP. Thus, the eukaryotic PanK has a distinct primary structure and unique regulatory properties that clearly distinguish it from its prokaryotic counterpart.
泛酸激酶（PanK）是辅酶A生物合成途径中的关键调节酶。此前已克隆出大肠杆菌的泛酸激酶基因（coaA），并对该酶进行了生化特性分析；其他原核生物中也存在高度相关的基因。我们通过对温度敏感型大肠杆菌泛酸激酶突变体进行功能互补，从真核真菌构巢曲霉中分离出一个泛酸激酶cDNA克隆。该cDNA克隆使得基因组克隆得以分离，并对构巢曲霉中名为panK的基因进行了特性分析。panK基因位于3号染色体（连锁群III）上，被三个小内含子打断，且组成性表达。构巢曲霉泛酸激酶（aPanK）的氨基酸序列预测其亚基大小为46.9 kDa，与细菌对应物几乎没有相似之处，而在酿酒酵母基因组中检测到一种高度相关的蛋白质。与受辅酶A调节且在较小程度上受其硫酯调节的大肠杆菌泛酸激酶（bPanK）不同，aPanK活性被乙酰辅酶A选择性且强力抑制。乙酰辅酶A对aPanK的抑制作用在ATP方面具有竞争性。因此，真核泛酸激酶具有独特的一级结构和独特的调节特性，使其与原核对应物明显区分开来。
