Discovery of a substrate selectivity motif in amino acid decarboxylases unveils a taurine biosynthesis pathway in prokaryotes.
Discovery of a substrate selectivity motif in amino acid decarboxylases unveils a taurine biosynthesis pathway in prokaryotes.
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DOI：
10.1021/cb400335k
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发表时间：
2013-10-18
影响因子：
4
通讯作者：
Stone, Everett M.
中科院分区：
文献类型：
--
作者：
Agnello, Giulia;Chang, Leslie L.;Lamb, Candice M.;Georgiou, George;Stone, Everett M.
牛磺酸是哺乳动物中含量最丰富的游离氨基酸，在神经元发育等方面具有重要作用，但迄今为止仅报道在真核生物中合成。牛磺酸是哺乳动物半胱氨酸代谢的主要产物，其生物合成途径包括半胱氨酸双加氧酶和半胱氨酸亚磺酸脱羧酶（hCSAD）。结构和顺序相关的hCSAD和人谷氨酸脱羧酶（hGAD）酶的序列，结构和突变分析揭示了三个残基底物识别基序（X1 aa 19 X2 aaX 3），在活性位点内负责协调各自的首选氨基酸底物。将半胱氨酸亚磺酸（CSA）基序引入hGAD（hGAD-S192 F/N212 S/F214 Y）中导致酶相对于其优选底物L-谷氨酸在CSA的脱羧选择性方面具有>700倍的转换。令人惊讶的是，我们在几种海洋细菌的基因组序列中发现了这种CSA识别基序，促使我们评估细菌氨基酸脱羧酶的催化特性，这些酶被序列基序预测为CSA脱羧，但被注释为GAD酶。我们表明，CSAD从聚球藻属PCC 7335特异性脱羧CSA和细菌积累细胞内牛磺酸。CSAD同源物存在于某些细菌中，并且经常在含有最近发现的将L-半胱氨酸氧化为CSA的细菌半胱氨酸双加氧酶的操纵子中发现，这一事实支持了真正的细菌牛磺酸生物合成途径存在于原核生物中的观点。
Taurine, the most abundant free amino acid in mammals, with many critical roles such as neuronal development, had so far only been reported to be synthetized in eukaryotes. Taurine is the major product of cysteine metabolism in mammals, and its biosynthetic pathway consists of cysteine dioxygenase and cysteine sulfinic acid decarboxylase (hCSAD). Sequence, structural, and mutational analyses of the structurally and sequentially related hCSAD and human glutamic acid decarboxylase (hGAD) enzymes revealed a three residue substrate recognition motif (X1aa19X2aaX3), within the active site that is responsible for coordinating their respective preferred amino acid substrates. Introduction of the cysteine sulfinic acid (CSA) motif into hGAD (hGAD-S192F/N212S/F214Y) resulted in an enzyme with a >700 fold switch in selectivity towards the decarboxylation of CSA over its preferred substrate, L-glutamic acid. Surprisingly, we found this CSA recognition motif in the genome sequences of several marine bacteria, prompting us to evaluate the catalytic properties of bacterial amino acid decarboxylases that were predicted by sequence motif to decarboxylate CSA but had been annotated as GAD enzymes. We show that CSAD from Synechococcus sp. PCC 7335 specifically decarboxylated CSA and that the bacteria accumulated intracellular taurine. The fact that CSAD homologues exist in certain bacteria and are frequently found in operons containing the recently discovered bacterial cysteine dioxygenases that oxidize L-cysteine to CSA, supports the idea that a bona fide bacterial taurine biosynthetic pathway exists in prokaryotes.
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影响因子：
3.3
作者：
OERTEL, WH;SCHMECHEL, DE;KOPIN, IJ
通讯作者：
KOPIN, IJ
影响因子：
11.4
作者：
Capitani, G;De Biase, D;Grütter, MG
通讯作者：
Grütter, MG
影响因子：
3.6
作者：
Cotter, PD;Gahan, CGM;Hill, C
通讯作者：
Hill, C
DOI：
10.1073/pnas.89.6.2115
发表时间：
1992-03-15
影响因子：
11.1
作者：
BU, DF;ERLANDER, MG;TOBIN, AJ
通讯作者：
TOBIN, AJ
影响因子：
56.9
作者：
Fagiolini, M;Fritschy, JM;Hensch, TK
通讯作者：
Hensch, TK