Pantoate Kinase and Phosphopantothenate Synthetase, Two Novel Enzymes Necessary for CoA Biosynthesis in the Archaea
Pantoate Kinase and Phosphopantothenate Synthetase, Two Novel Enzymes Necessary for CoA Biosynthesis in the Archaea
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DOI：
10.1074/jbc.m109.009696
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发表时间：
2009-10-09
影响因子：
4.8
通讯作者：
Imanaka, Tadayuki
中科院分区：
文献类型：
--
作者：
Yokooji, Yuusuke;Tomita, Hiroya;Imanaka, Tadayuki
细菌/真核生物具有共同的辅酶A(CoA)合成途径。尽管古生菌基因组中含有大多数这些酶的同源物，但细菌/真核生物泛酸合成酶(PS)和泛酸激酶(PANK)的同源物却缺失。PS催化泛酸和β-丙氨酸依赖于ATP的缩合反应生成泛酸，而Pank催化依赖于ATP的泛酸磷酸化生成4‘-磷酸泛酸。当我们检测高温考古菌的无细胞提取物时，没有检测到Pank活性。对广泛分布于古生代但在细菌/真核生物中不存在的假定的激酶编码基因的搜索，导致了四个候选基因。在这些基因中，TK2141编码一种Pank活性相对较低的蛋白。然而，当泛酸盐被泛酸盐取代时，观察到更高的活性水平。对泛酸的V-max值高出7倍，表明TK2141编码了一种新的酶-泛酸激酶(POK)。对与TK2141具有相似分布的基因的搜索导致了TK1686的鉴定。该蛋白产物催化磷酸泛酸和β-丙氨酸依赖于ATP的转化生成4‘-磷酸泛酸，不显示PS活性，表明TK1686还编码了一种新的酶，即磷酸泛酸合成酶(PPS)。虽然经典的PS/PANK体系在磷酸化之前与β-丙氨酸进行缩合，但POK/PPS体系在泛酸磷酸化之后进行缩合。TK2141和TK1686基因突变导致辅酶A营养不良，表明这两个基因是柯达卡拉氏木霉辅酶A生物合成所必需的。这两个基因的同源基因在古生菌中广泛分布，这表明POK/PPS系统代表了古生菌中4‘-磷酸泛酸生物合成的途径。
Bacteria/eukaryotes share a common pathway for coenzyme A (CoA) biosynthesis. Although archaeal genomes harbor homologs for most of these enzymes, homologs of bacterial/eukaryotic pantothenate synthetase (PS) and pantothenate kinase (PanK) are missing. PS catalyzes the ATP-dependent condensation of pantoate and beta-alanine to produce pantothenate, whereas PanK catalyzes the ATP-dependent phosphorylation of pantothenate to produce 4'-phosphopantothenate. When we examined the cell-free extracts of the hyperthermophilic archaeon Thermococcus kodakaraensis, PanK activity could not be detected. A search for putative kinase-encoding genes widely distributed in Archaea, but not present in bacteria/eukaryotes, led to four candidate genes. Among these genes, TK2141 encoded a protein with relatively low PanK activity. However, higher levels of activity were observed when pantothenate was replaced with pantoate. V-max values were 7-fold higher toward pantoate, indicating that TK2141 encoded a novel enzyme, pantoate kinase (PoK). A search for genes with a distribution similar to TK2141 led to the identification of TK1686. The protein product catalyzed the ATP-dependent conversion of phosphopantoate and beta-alanine to produce 4'-phosphopantothenate and did not exhibit PS activity, indicating that TK1686 also encoded a novel enzyme, phosphopantothenate synthetase (PPS). Although the classic PS/PanK system performs condensation with beta-alanine prior to phosphorylation, the PoK/PPS system performs condensation after phosphorylation of pantoate. Gene disruption of TK2141 and TK1686 led to CoA auxotrophy, indicating that both genes are necessary for CoA biosynthesis in T. kodakaraensis. Homologs of both genes are widely distributed among the Archaea, suggesting that the PoK/PPS system represents the pathway for 4'-phosphopantothenate biosynthesis in the Archaea.