大肠杆菌4-氨基-4-脱氧胆酸裂解酶的三维结构,The Journal of Biochemistry

当前位置： X-MOL 学术 › J. Biochem. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

大肠杆菌4-氨基-4-脱氧胆酸裂解酶的三维结构
The Journal of Biochemistry ( IF 2.1 ) Pub Date : 2000-07-01 , DOI: 10.1093/oxfordjournals.jbchem.a022727
T. Nakai , H. Mizutani , I. Miyahara , K. Hirotsu , S. Takeda , K.-H. Jhee , T. Yoshimura , N. Esaki

4-氨基-4-脱氧胆酸酯裂解酶（ADCL）是PLP依赖性酶的折叠类型IV的成员，该酶将4-氨基-4-脱氧胆酸酯（ADC）转换为对氨基苯甲酸酯和丙酮酸。使用MIR相结合密度修饰已解决了来自大肠杆菌的ADCL的晶体结构。该结构在2.2 A分辨率下已精炼到20.6％的R系数。该酶是具有结晶学双重轴的同型二聚体，并且多肽链通过域间环折叠成小域和大域。辅酶5'-磷酸吡ido醛位于结构域界面，其背面朝向蛋白质。尽管活性位点的主链折叠与D-氨基酸和L-支链氨基酸氨基转移酶的同源，除了Arg59，Lys159和Glu193，它们与活性酶直接相互作用并在催化功能中起关键作用，在活性位点中没有保守的残基。根据D-氨基酸和L-支链氨基酸氨基转移酶中未配体和配体形式的X射线结构，将ADC建模到未配体酶的活性位点中。根据该模型，ADC的羧酸盐被Asn256，Arg107和Lys97识别，并且环己二烯部分使范德华斯与Leu258的侧链接触。ADC与PLP形成席夫碱，释放出催化残基Lys159，后者与Thr38形成氢键。

"点击查看英文标题和摘要"

Three-Dimensional Structure of 4-Amino-4-Deoxychorismate Lyase from Escherichia coli

4-Amino-4-deoxychorismate lyase (ADCL) is a member of the fold-type IV of PLP dependent enzymes that converts 4-amino-4-deoxychorismate (ADC) to p-aminobenzoate and pyruvate. The crystal structure of ADCL from Escherichia coli has been solved using MIR phases in combination with density modification. The structure has been refined to an R-factor of 20.6% at 2.2 A resolution. The enzyme is a homo dimer with a crystallographic twofold axis, and the polypeptide chain is folded into small and large domains with an interdomain loop. The coenzyme, pyridoxal 5'-phosphate, resides at the domain interface, its re-face facing toward the protein. Although the main chain folding of the active site is homologous to those of D-amino acid and L-branched-chain amino acid aminotransferases, no residues in the active site are conserved among them except for Arg59, Lys159, and Glu193, which directly interact with the coenzyme and play critical roles in the catalytic functions. ADC was modeled into the active site of the unliganded enzyme on the basis of the X-ray structures of the unliganded and liganded forms in the D-amino acid and L-branched-chain amino acid aminotransferases. According to this model, the carboxylates of ADC are recognized by Asn256, Arg107, and Lys97, and the cyclohexadiene moiety makes van der Waals contact with the side chain of Leu258. ADC forms a Schiff base with PLP to release the catalytic residue Lys159, which forms a hydrogen bond with Thr38. The neutral amino group of Lys159 eliminates the a-proton of ADC to give a quinonoid intermediate to release a pyruvate in accord with the proton transfer from Thr38 to the olefin moiety of ADC.

更新日期：2000-07-01

点击分享查看原文

点击收藏

阅读更多本刊新发论文