Comprehensive X-ray structural studies of the quinolinate phosphoribosyl transferase (BNA6) from Saccharomyces cerevisiae
Comprehensive X-ray structural studies of the quinolinate phosphoribosyl transferase (BNA6) from Saccharomyces cerevisiae
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DOI：
10.1021/bi7020475
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发表时间：
2008-04-01
期刊：
影响因子：
2.9
通讯作者：
Wilson, David K.
中科院分区：
文献类型：
--
作者：
Di Luccio, Eric;Wilson, David K.
喹啉酸磷酸核糖基转移酶（QAPRTase，EC 2.4.2.19）是由酵母中的BNA 6基因编码的32 kDa酶，并且催化由喹啉酸和5-磷酸核糖基-1-焦磷酸（PRPP）形成烟酸单核苷酸酯。QAPRTase通过犬尿氨酸在色氨酸降解途径中发挥关键作用，导致NAD（+）的从头生物合成并清除神经毒素喹啉酸。为了提高我们对真核生物酶的特异性和与催化相关的事件过程的理解，我们已经确定了载脂蛋白和底物喹啉酸盐和PRPP的单一结合形式的晶体结构。这揭示了该酶以类似于各种原核形式的方式折叠，其在序列上类似于30%相同。此外，米氏络合物的结构近似于PRPP和与活性位点结合的喹啉类似物邻苯二甲酸酯。这些结果允许深入了解QAPRTase的动力学机制，并提供了一个结构多样性的酿酒酵母酶的活性位点相比，原核同源物。
Quinolinic acid phosphoribosyl transferase (QAPRTase, EC 2.4.2.19) is a 32 kDa enzyme encoded by the BNA6 gene in yeast and catalyzes the formation of nicotinate mononucleotide from quinolinate and 5-phosphoribosyl-1-pyrophosphate (PRPP). QAPRTase plays a key role in the tryptophan degradation pathway via kynurenine, leading to the de novo biosynthesis of NAD(+) and clearing the neurotoxin quinolinate. To improve our understanding of the specificity of the eukaryotic enzyme and the course of events associated with catalysis, we have determined the crystal structures of the apo and singly bound forms with the substrates quinolinate and PRPP. This reveals that the enzyme folds in a manner similar to that of various prokaryotic forms which are similar to 30% identical in sequence. In addition, the structure of the Michaelis complex is approximated by PRPP and the quinolinate analogue phthalate bound to the active site. These results allow insight into the kinetic mechanism of QAPRTase and provide an understanding of structural diversity in the active site of the Saccharomyces cerevisiae enzyme when compared to prokaryotic homologues.