Acetobacter turbidans α-amino acid ester hydrolase -: How a single mutation improves an antibiotic-producing enzyme
Acetobacter turbidans α-amino acid ester hydrolase -: How a single mutation improves an antibiotic-producing enzyme
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DOI：
10.1074/jbc.m511187200
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发表时间：
2006-03-03
影响因子：
4.8
通讯作者：
Dijkstra, BW
中科院分区：
文献类型：
--
作者：
Barends, TRM;Polderman-Tijmes, JJ;Dijkstra, BW
浑浊醋杆菌的α-氨基酸酯水解酶（AEH）是一种催化β-内酰胺类抗生素水解和合成的细菌酶。天然酶的晶体结构，无论是unliganded和与水解产物D-苯基甘氨酸的复合物，以及与底物氨苄青霉素复合的无活性突变体（S205 A）的结构，和活性位点突变体（Y206 A）具有增加的倾向，催化抗生素的生产，而不是水解。天然酶的结构显示出酰基结合口袋，其中D-苯甘氨酸结合，以及足够大以容纳抗生素的β-内酰胺部分的额外空间。在S205 A突变体中，氨苄青霉素以非生产性方式结合在该口袋中，与Tyr（112）的侧链广泛接触，其也参与氧阴离子空穴形成。在Y206 A突变体中，Tyr（112）侧链与其羟基一起向催化丝氨酸移动。因为这改变了β-内酰胺结合位点的性质，这可以解释该突变体的β-内酰胺转移酶活性增加。
The alpha- amino acid ester hydrolase ( AEH) from Acetobacter turbidans is a bacterial enzyme catalyzing the hydrolysis and synthesis of beta- lactam antibiotics. The crystal structures of the native enzyme, both unliganded and in complex with the hydrolysis product D- phenylglycine are reported, as well as the structures of an inactive mutant ( S205A) complexed with the substrate ampicillin, and an active site mutant ( Y206A) with an increased tendency to catalyze antibiotic production rather than hydrolysis. The structure of the native enzyme shows an acyl binding pocket, in which D- phenylglycine binds, and an additional space that is large enough to accommodate the beta- lactam moiety of an antibiotic. In the S205A mutant, ampicillin binds in this pocket in a non- productive manner, making extensive contacts with the side chain of Tyr(112), which also participates in oxyanion hole formation. In the Y206A mutant, the Tyr(112) side chain has moved with its hydroxyl group toward the catalytic serine. Because this changes the properties of the beta- lactam binding site, this could explain the increased beta- lactam transferase activity of this mutant.